Evolution Essay

Evolution Essay

Evolution is the theory that all living forms came from ancient ancestors. Through a series of mutations, genetic drift, migration, and natural selection today’s descendants show an amazing amount of similarities and diversity. Evolution on a small scale is called microevolution, relating to the changes that occur such as insects becoming resistant to pesticides. Macroevolution refers to the grand scale. It is associated with extinction, change, stability, and lineage. At the time of its “birth”, it was a controversial subject. Charles Darwin was the first to formalize the theory of evolution, but before him there were more scientists interested in it.

Charles Darwin was born in England and originally planned to take up a career in medicine. When that didn’t work out, he switched to divinity in Cambridge. Later he took a five year excursion on the HMS Beagle. During his time on board Darwin read the “Principles of Geology” that stated there was geological evidence of ancient animals. While on the Galapagos Islands he noticed that the finches on the each island were closely related but different in big ways. When he returned, he theorized evolution based on natural selection. Twenty years later he and Alfred Russell Wallace discussed evolution openly. In 1859 he published his extremely controversial ideas. Darwin was attacked for his theory, particularly by the Church. But his ideas became widely accepted.

Darwin’s own grandfather, Erasmus Darwin, was a prestigious physician, botanist, naturalist, poet, and philosopher. He believed that all modern creatures had originated from “one living filament”, a common ancestor. Erasmus did not come up with natural selection, but he did believe in competition and sexual selection. He believed that the strongest males reserved the right to mate, therefore passing on satisfactory traits. He used an integrative method of research, bringing together multiple branches of science to come to his conclusion. Some of his ideas were alike to those of Jean Baptiste Lamarck. Lamarck is an obscure character in evolutionary history as he was ostracized and his theories were not recognized by his colleagues. He was in the army, then worked as a botanist in the royal gardens. In 1793, Lamarck was appointed professor of invertebrates. At the time there was little research on insects. He wrote a series of books about invertebrate zoology and paleontology. Although other scientists in his day hinted at the possibility of evolution, Lamarck declared it forthright. He was discredited by his peers and died a poor man. However, Charles Darwin and others respected his as a great zoologist and the forerunner of evolutionary theory. Georges Cuvier was a colleague of Lamarck’s that forsake him. He was a brilliant mind, but he did not share Lamarck’s theory of evolution, going as far as to discredit him. Cuvier had studied mummies of cats and ibises brought back from Egypt by Napoleon. Finding no difference from current day animals, he had decided evolution was false. He later studied elephants and mammoth fossils, determining that mammoths were different from living elephants in their day. This led to the important idea of extinction.

Macroevolution is evolution on a grand scale. Instead of focusing on a single branch, macroevolution focuses on that chunk of the tree. It identifies patterns and transformations, then figures out how and why it happened. Mutation, migration, genetic drift, and natural selection are basic mechanisms that apply to both micro- and macroevolution to determine these patterns.For 3.8 billion years mutations have been passing through the filter of natural selection, creating stronger and more resilient descendants.  Changes and extinctions that have happened over the years are all part of macroevolution. Some changes take place slowly, this is called stasis. An example of this is the cœlacanth, a fish hauled onto a ship in 1938, it was thought to be extinct for 70 million years. Extinction is an important part of evolution. Every species has a chance that it will become extinct. Microevolution is an even more important part of the evolutionary theory. As previously discussed, it is evolution on a small scale. It is the changes in animals to adapt to their habitats and the changing environment. Microevolutionairy changes can be seen by changes in gene frequency. A few of the mechanisms that affect these changes are mutation, migration, genetic drift, and natural selection. If a random cell is mutated, for example if a  yellow bird has some purple chicks and the rest are yellow. The genes in the yellow bird would have been mutated to produce purple chicks. If the purple chicks moved to another island, and the yellow birds on that island immigrated to the island that purple birds had previously inhabited, that is known at migration, or gene flow. When a mutated gene is passed to more offspring and out numbers the original colored offspring it is called genetic drift. As for natural selection, it means that the more well equipped animals are the most likely to survive. For example if the purple birds lived in a purple tree they would be more likely to survive than their yellow relatives in a purple tree. A test for preformed on sand colored and dark colored mice, showing that each mouse matched the color of their corresponding habitats. When put in the other’s habitat, they were put into more danger.

Ideas about evolution extend to different types of science as well. Biochemistry is also interested in this topic. It shows that there is a surprising amount of evolutionary evidence within the human body, bacteria, and fungus. An e.coli bacteria can become mutated and glow under a black light, showing an evolutionary change. As human fetuses grow within their mother’s wombs they are changing in evolutionary ways. There is fossil evidence that supports the evolutionary theory. Paleontologists have found and studied different species of fossils and have concluded that some fossils found were related to fossils found prior to the dig, or after. These fossils just had changes to them, evolution it could be said.

The most convincing arguments for evolution seem to be fossil evidence and the evidence that the fossils have evolved from other, previous fossils. Seeing how Darwin’s finches different from each other although they are the same bird, it makes sense to believe that evolution is plausible. Human are even evolving. Jaws are becoming shorter and their is less room for wisdom teeth in their mouths. Looking back into history, there is also the thought about Native Americans who lived in Arizona or the indigenous people of the Arctic. Their constitutions must have been completely different to be able to survive such extreme conditions. When thinking about dogs, crows, and spiders that can procreate with different dogs, crows, and spiders in their species it’s hard not to believe in evolution. This idea of speciation is a rather convincing idea.

Different Diseases and Syndromes

Wrinkles

Wrinkles is not a disease nor any virus or bacteria but wrinkle appears on a human being as well as on animals as the age passes through, wrinkles are also considered as the sign of maturity, these wrinkles are also seen on the fingers when a person take more time in swimming pool or water.

Causes of Wrinkles:

* The main cause is the age factor and majority of people get wrinkles on skin when they cross 60-65 years of age.
* Smoking is another cause of having wrinkles on skin.
* Taking enough sun bath can also cause it.
* Heredity.
* Drinking less amount of water.
* People who works in sun exposure areas like golf course, grounds often get wrinkles.

How to prevent Wrinkles:

One should follow these steps in order to stay away with it.
*  One should use full sleeves shirts, hats or caps and other necessary dress which can prevent from direct sun light.
* Quit smoking as it is cause of dozens of other dangerous diseases as well.
* Drink enough water so that your skin does not get dry and can dehydration.

Wrinkles Treatment:

The wrinkles treatment include some creams and medicines, you cannot say that you can 100% get rid of these wrinkles but some.

Marfan Syndrome

Marfan syndrome is an inherited disease which damages the connective tissue of the body. the most abundant tissue in the body are the connective tissues and is a vital component to supporting the body's organs.
It provide the body with support and strength to tendons, cartilages, heart valves, and to many other parts of the body, another main function of connective tissues is to strengthen and elasticity of blood valves.
Because the connective tissues are present in the whole body, Marfan syndrome can affect many parts, including the bones, skin, heart and blood vessels, nervous system, lungs and eyes.one of its major effected part  is aorta it can badly effect aorta.

Causes of Marfan Syndrome:

1. It is caused due to defect in gene.
2. Mostly this disease is inherited. It can take place similarly in men and women and can be inherited from only one parent having this marfan syndrome disease.

Diagnosis of Marfan Syndrome

:
1. The doctors or experts can take physical exam of eyes, heart, muscle, blood vessels and of skeletal system.
2. They also can take the ECG (electrocardiogram), some x-rays like Chest X-Ray, Echocardiogram and some other tests like CT-Scan and MRI, because they are helpful in diagnosing this disease.

Symptoms of Marfan Syndrome:

The symptoms of marfan syndrome are not yet clearly known but their are some signs through which one can feel it like a person feeling gracelessness in bones, some organs of body not functioning properly, In some cases a person feels fatigue,pain throughout the body or in some organs, loss of appetite and heart blockage.

Rosacea

Rosacea is another disease of skin which causes redness and pimples on the body of human being and specially it appears on  forehead , cheeks, chin, and nose parts. This redness can frequently appear or suddenly disappear. Specialists also call rosacea as "adult acne" because rosacea may cause outbreaks which looks same like acne.
It can be embarrassing sometimes or in the case it is untreated than it will get worst and worst day by day.

Causes of Rosacea:
1. Its main causes are unknown up till now.
2. It may be genetically.
3. Those people who are infected by complexion are seem to be more are seem to be more infected by rosacea.
4. Rosacea often happens when something causes the blood vessels in the face to expand, which causes redness on face.

Symptoms of Rosacea:
1. The red veins which are present on the skin of a person are clearly seen like the web of a spider.
2. Flushed face.
3. Feeling hot or burning on the skin.
4. Itching
5. Itching or sensations on the skin whenever victim apply creams, lotions or medicines.

Treatment of Rosacea:
1. Antibiotics may help.
2. Antibiotic creams are also advised by experts.
3. Surgery may help.
4. Some creams or soaps may be advised by the experts.
5. No one should use severly hot water on body it will result in dryness and can get effected by rosacea.

Graves Disease

Graves disease is a thyroid condition which affects the gland in a way that the gland results in abnormal over activity and the thyroid of a person starts producing huge amount of hormones.This disease is one of the main cause of hyperthyroidism, it includes nervousness, anxiety, fatigue, bulging eyes, weight loss, hypertension and irritability. Sometimes the complications may lead to life threatening risks.
Graves' disease is more common in women than in men specially in USA. People over the age of 50 who have hypertension or atherosclerosis are at severe risk for developing Graves' disease. Graves' disease is also the most common autoimmune diseases, affecting 13 million people and targeting women seven times as often as men.

Symptoms of Grave’s Disease:


1. Shaky hands.
2. Diarrhea.
3. Weight loss.
4. Tremors.
5. Lack of sleep.
6. Sweating.
7. Fatigue.
8. Irritability.
9. Rapid heart rate.

Diagnosis of Grave’s disease:


A blood test is usually performed to check levels of thyroid stimulating hormone (TSH) and the thyroid hormone thyroxine. If Low levels of TSH and high levels of thyroxine is found then only this disease can be diagnosed.

Treatment of grave's disease:


There is no way to prevent Graves' disease, high level of thyroid glands can be rolled back to the normal level taking regular medicines and by monitoring disease.

Adenoma

Adenoma is a benign tumor that develops from epithelial tissues, it is also found in colon it is often referred to as adenomatous polyps, mostly adenomas are not cancerous but they have ability to become cancerous. No doubt they left a noticeable effect where ever they target in the body that organ show that it is affected by adenoma and is quite uncomfortable for the individual. There are many types of adenomas that are common in women, such as adenomas of liver, colon adenoma which is more common in adults of growing age.

Causes of Adenoma:

The cause of adenoma are yet unknown.

Types of Adenoma:

There are three types of adenomas:
1. Tubular.
2. Tubulovillous.
3. Villous.

Symptoms of Adenoma:

1. Bloody cough.
2. Itching.
3. Bleeding.
4. Shortness of breath.
5. Chills.
6. Fatigue.
There are many unfound symptoms of this disease as well.
There could be many other unknown and unseen symptoms as well that can be seen vary widely.

Diagnosis of Adenoma:

1. By collecting urine samples.
2. By blood tests.
3. Ultra sound imaging.
4. CT scan.
5. Biopsy.
6. MRI.

Treatment of Adenoma:

The treatment usually involves the removal of adenoma although such types of medication can also be used to treat symptoms of this disease as well.

What is Biotechnology? and history

What is Biotechnology?


Pamela Peters, from Biotechnology: A Guide To Genetic Engineering. Wm. C. Brown Publishers, Inc., 1993.

Biotechnology is technology based on biology, especially when used in agriculture, food science, and medicine. The United Nations Convention on Biological Diversity defines biotechnology as

Biotechnology in one form or another has flourished since prehistoric times. When the first human beings realized that they could plant their own crops and breed their own animals, they learned to use biotechnology. The discovery that fruit juices fermented into wine, or that milk could be converted into cheese or yogurt, or that beer could be made by fermenting solutions of malt and hops began the study of biotechnology. When the first bakers found that they could make a soft, spongy bread rather than a firm, thin cracker, they were acting as fledgling biotechnologists. The first animal breeders, realizing that different physical traits could be either magnified or lost by mating appropriate pairs of animals, engaged in the manipulations of biotechnology.

What then is biotechnology? The term brings to mind many different things. Some think of developing new types of animals. Others dream of almost unlimited sources of human therapeutic drugs. Still others envision the possibility of growing crops that are more nutritious and naturally pest-resistant to feed a rapidly growing world population. This question elicits almost as many first-thought responses as there are people to whom the question can be posed.

In its purest form, the term "biotechnology" refers to the use of living organisms or their products to modify human health and the human environment. Prehistoric biotechnologists did this as they used yeast cells to raise bread dough and to ferment alcoholic beverages, and bacterial cells to make cheeses and yogurts and as they bred their strong, productive animals to make even stronger and more productive offspring.

Throughout human history, we have learned a great deal about the different organisms that our ancestors used so effectively. The marked increase in our understanding of these organisms and their cell products gains us the ability to control the many functions of various cells and organisms. Using the techniques of gene splicing and recombinant DNA technology, we can now actually combine the genetic elements of two or more living cells. Functioning lengths of DNA can be taken from one organism and placed into the cells of another organism. As a result, for example, we can cause bacterial cells to produce human molecules. Cows can produce more milk for the same amount of feed. And we can synthesize therapeutic molecules that have never before existed.


HISTORY

The most practical use of biotechnology, which is still present today, is the cultivation of plants to produce food suitable to humans. Agriculture has been theorized to have become the dominant way of producing food since the Neolithic Revolution. The processes and methods of agriculture have been refined by other mechanical and biological sciences since its inception. Through early biotechnology farmers were able to select the best suited and highest-yield crops to produce enough food to support a growing population. Other uses of biotechnology were required as crops and fields became increasingly large and difficult to maintain. Specific organisms and organism byproducts were used to fertilize, restore nitrogen, and control pests. Throughout the use of agriculture farmers have inadvertently altered the genetics of their crops through introducing them to new environments and breeding them with other plants--one of the first forms of biotechnology. Cultures such as those in Mesopotamia, Egypt, and India developed the process of brewing beer. It is still done by the same basic method of using malted grains (containing enzymes) to convert starch from grains into sugar and then adding specific yeasts to produce beer. In this process the carbohydrates in the grains were broken down into alcohols such as ethanol. Ancient Indians also used the juices of the plant Ephedra Vulgaris and used to call it Soma. Later other cultures produced the process of Lactic acid fermentation which allowed the fermentation and preservation of other forms of food. Fermentation was also used in this time period to produce leavened bread. Although the process of fermentation was not fully understood until Louis Pasteur’s work in 1857, it is still the first use of biotechnology to convert a food source into another form.

Combinations of plants and other organisms were used as medications in many early civilizations. Since as early as 200 BC, people began to use disabled or minute amounts of infectious agents to immunize themselves against infections. These and similar processes have been refined in modern medicine and have led to many developments such as antibiotics, vaccines, and other methods of fighting sickness.

In the early twentieth century scientists gained a greater understanding of microbiology and explored ways of manufacturing specific products. In 1917, Chaim Weizmann first used a pure microbiological culture in an industrial process, that of manufacturing corn starch using Clostridium acetobutylicum to produce acetone, which the United Kingdom desperately needed to manufacture explosives during World War I.

The field of modern biotechnology is thought to have largely begun on June 16, 1980, when the United States Supreme Court ruled that a genetically-modified microorganism could be patented in the case of Diamond v. Chakrabarty. Indian-born Ananda Chakrabarty, working for General Electric, had developed a bacterium (derived from the Pseudomonas genus) capable of breaking down crude oil, which he proposed to use in treating oil spills.

Revenue in the industry is expected to grow by 12.9% in 2008. Another factor influencing the biotechnology sector's success is improved intellectual property rights legislation -- and enforcement -- worldwide, as well as strengthened demand for medical and pharmaceutical products to cope with an ageing, and ailing, U.S. population .

Rising demand for biofuels is expected to be good news for the biotechnology sector, with the Department of Energy estimating ethanol usage could reduce U.S. petroleum-derived fuel consumption by up to 30% by 2030. The biotechnology sector has allowed the U.S. farming industry to rapidly increase its supply of corn and soybeans -- the main inputs into biofuels -- by developing genetically-modified seeds which are resistant to pests and drought. By boosting farm productivity, biotechnology plays a crucial role in ensuring that biofuel production targets are met.

Applications of biotechnology

Applications of biotechnology

Applications

Biotechnology has applications in four major industrial areas, including health care (medical), crop production and agriculture, non food (industrial) uses of crops and other products (e.g. biodegradable plastics, vegetable oil, biofuels), and environmental uses.

For example, one application of biotechnology is the directed use of organisms for the manufacture of organic products (examples include beer and milk products). Another example is using naturally present bacteria by the mining industry in bioleaching. Biotechnology is also used to recycle, treat waste, clean up sites contaminated by industrial activities (bioremediation), and also to produce biological weapons.

A series of derived terms have been coined to identify several branches of biotechnology, for example:
Red biotechnology is applied to medical processes. Some examples are the designing of organisms to produce antibiotics, and the engineering of genetic cures through genomic manipulation.
A rose plant that began as cells grown in a tissue culture
Green biotechnology is biotechnology applied to agricultural processes. An example would be the selection and domestication of plants via micropropagation. Another example is the designing of transgenic plants to grow under specific environmental conditions or in the presence (or absence) of certain agricultural chemicals. One hope is that green biotechnology might produce more environmentally friendly solutions than traditional industrial agriculture. An example of this is the engineering of a plant to express a pesticide, thereby eliminating the need for external application of pesticides. An example of this would be Bt corn. Whether or not green biotechnology products such as this are ultimately more environmentally friendly is a topic of considerable debate.
White biotechnology, also known as industrial biotechnology, is biotechnology applied to industrial processes. An example is the designing of an organism to produce a useful chemical. Another example is the using of enzymes as industrial catalysts to either produce valuable chemicals or destroy hazardous/polluting chemicals. White biotechnology tends to consume less in resources than traditional processes used to produce industrial goods.
Blue biotechnology is a term that has been used to describe the marine and aquatic applications of biotechnology, but its use is relatively rare.
The investments and economic output of all of these types of applied biotechnologies form what has been described as the bioeconomy.
Bioinformatics is an interdisciplinary field which addresses biological problems using computational techniques, and makes the rapid organization and analysis of biological data possible. The field may also be referred to as computational biology, and can be defined as, "conceptualizing biology in terms of molecules and then applying informatics techniques to understand and organize the information associated with these molecules, on a large scale." Bioinformatics plays a key role in various areas, such as functional genomics, structural genomics, and proteomics, and forms a key component in the biotechnology and pharmaceutical sector.

Medicine


In medicine, modern biotechnology finds promising applications in such areas as
pharmacogenomics;
drug production;
genetic testing; and
gene therapy.

Pharmacogenomics


DNA Microarray chip -- Some can do as many as a million blood tests at once
Main article: Pharmacogenomics

Pharmacogenomics is the study of how the genetic inheritance of an individual affects his/her body’s response to drugs. It is a coined word derived from the words “pharmacology” and “genomics”. It is hence the study of the relationship between pharmaceuticals and genetics. The vision of pharmacogenomics is to be able to design and produce drugs that are adapted to each person’s genetic makeup.

Pharmacogenomics results in the following benefits:

1. Development of tailor-made medicines. Using pharmacogenomics, pharmaceutical companies can create drugs based on the proteins, enzymes and RNA molecules that are associated with specific genes and diseases. These tailor-made drugs promise not only to maximize therapeutic effects but also to decrease damage to nearby healthy cells.

2. More accurate methods of determining appropriate drug dosages. Knowing a patient’s genetics will enable doctors to determine how well his/ her body can process and metabolize a medicine. This will maximize the value of the medicine and decrease the likelihood of overdose.

3. Improvements in the drug discovery and approval process. The discovery of potential therapies will be made easier using genome targets. Genes have been associated with numerous diseases and disorders. With modern biotechnology, these genes can be used as targets for the development of effective new therapies, which could significantly shorten the drug discovery process.

4. Better vaccines. Safer vaccines can be designed and produced by organisms transformed by means of genetic engineering. These vaccines will elicit the immune response without the attendant risks of infection. They will be inexpensive, stable, easy to store, and capable of being engineered to carry several strains of pathogen at once.

Pharmaceutical products
Computer-generated image of insulin hexamers highlighting the threefold symmetry, the zinc ions holding it together, and the histidine residues involved in zinc binding.

Most traditional pharmaceutical drugs are relatively simple molecules that have been found primarily through trial and error to treat the symptoms of a disease or illness. Biopharmaceuticals are large biological molecules known as proteins and these usually target the underlying mechanisms and pathways of a malady (but not always, as is the case with using insulin to treat type 1 diabetes mellitus, as that treatment merely addresses the symptoms of the disease, not the underlying cause which is autoimmunity); it is a relatively young industry. They can deal with targets in humans that may not be accessible with traditional medicines. A patient typically is dosed with a small molecule via a tablet while a large molecule is typically injected.

Small molecules are manufactured by chemistry but larger molecules are created by living cells such as those found in the human body: for example, bacteria cells, yeast cells, animal or plant cells.

Modern biotechnology is often associated with the use of genetically altered microorganisms such as E. coli or yeast for the production of substances like synthetic insulin or antibiotics. It can also refer to transgenic animals or transgenic plants, such as Bt corn. Genetically altered mammalian cells, such as Chinese Hamster Ovary (CHO) cells, are also used to manufacture certain pharmaceuticals. Another promising new biotechnology application is the development of plant-made pharmaceuticals.

Biotechnology is also commonly associated with landmark breakthroughs in new medical therapies to treat hepatitis B, hepatitis C, cancers, arthritis, haemophilia, bone fractures, multiple sclerosis, and cardiovascular disorders. The biotechnology industry has also been instrumental in developing molecular diagnostic devices than can be used to define the target patient population for a given biopharmaceutical. Herceptin, for example, was the first drug approved for use with a matching diagnostic test and is used to treat breast cancer in women whose cancer cells express the protein HER2.

Modern biotechnology can be used to manufacture existing medicines relatively easily and cheaply. The first genetically engineered products were medicines designed to treat human diseases. To cite one example, in 1978 Genentech developed synthetic humanized insulin by joining its gene with a plasmid vector inserted into the bacterium Escherichia coli. Insulin, widely used for the treatment of diabetes, was previously extracted from the pancreas of abattoir animals (cattle and/or pigs). The resulting genetically engineered bacterium enabled the production of vast quantities of synthetic human insulin at relatively low cost, although the cost savings was used to increase profits for manufacturers, not passed on to consumers or their healthcare providers. According to a 2003 study undertaken by the International Diabetes Federation (IDF) on the access to and availability of insulin in its member countries, synthetic 'human' insulin is considerably more expensive in most countries where both synthetic 'human' and animal insulin are commercially available: e.g. within European countries the average price of synthetic 'human' insulin was twice as high as the price of pork insulin. Yet in its position statement, the IDF writes that "there is no overwhelming evidence to prefer one species of insulin over another" and "[modern, highly-purified] animal insulins remain a perfectly acceptable alternative.

Modern biotechnology has evolved, making it possible to produce more easily and relatively cheaply human growth hormone, clotting factors for hemophiliacs, fertility drugs, erythropoietin and other drugs.[12] Most drugs today are based on about 500 molecular targets. Genomic knowledge of the genes involved in diseases, disease pathways, and drug-response sites are expected to lead to the discovery of thousands more new targets

Genetic testing

Gel electrophoresis

Genetic testing involves the direct examination of the DNA molecule itself. A scientist scans a patient’s DNA sample for mutated sequences.

There are two major types of gene tests. In the first type, a researcher may design short pieces of DNA (“probes”) whose sequences are complementary to the mutated sequences. These probes will seek their complement among the base pairs of an individual’s genome. If the mutated sequence is present in the patient’s genome, the probe will bind to it and flag the mutation. In the second type, a researcher may conduct the gene test by comparing the sequence of DNA bases in a patient’s gene to disease in healthy individuals or their progeny.

Genetic testing is now used for:
Determining sex
Carrier screening, or the identification of unaffected individuals who carry one copy of a gene for a disease that requires two copies for the disease to manifest
Prenatal diagnostic screening
Newborn screening
Presymptomatic testing for predicting adult-onset disorders
Presymptomatic testing for estimating the risk of developing adult-onset cancers
Confirmational diagnosis of symptomatic individuals
Forensic/identity testing





Some genetic tests are already available, although most of them are used in developed countries. The tests currently available can detect mutations associated with rare genetic disorders like cystic fibrosis, sickle cell anemia, and Huntington’s disease. Recently, tests have been developed to detect mutation for a handful of more complex conditions such as breast, ovarian, and colon cancers. However, gene tests may not detect every mutation associated with a particular condition because many are as yet undiscovered, and the ones they do detect may present different risks to different people and populations.

Controversial questions

The bacterium E. coli is routinely genetically engineered.

Several issues have been raised regarding the use of genetic testing:

1. Absence of cure. There is still a lack of effective treatment or preventive measures for many diseases and conditions now being diagnosed or predicted using gene tests. Thus, revealing information about risk of a future disease that has no existing cure presents an ethical dilemma for medical practitioners.

2. Ownership and control of genetic information. Who will own and control genetic information, or information about genes, gene products, or inherited characteristics derived from an individual or a group of people like indigenous communities? At the macro level, there is a possibility of a genetic divide, with developing countries that do not have access to medical applications of biotechnology being deprived of benefits accruing from products derived from genes obtained from their own people. Moreover, genetic information can pose a risk for minority population groups as it can lead to group stigmatization.

At the individual level, the absence of privacy and anti-discrimination legal protections in most countries can lead to discrimination in employment or insurance or other misuse of personal genetic information. This raises questions such as whether genetic privacy is different from medical privacy.

3. Reproductive issues. These include the use of genetic information in reproductive decision-making and the possibility of genetically altering reproductive cells that may be passed on to future generations. For example, germline therapy forever changes the genetic make-up of an individual’s descendants. Thus, any error in technology or judgment may have far-reaching consequences. Ethical issues like designer babies and human cloning have also given rise to controversies between and among scientists and bioethicists, especially in the light of past abuses with eugenics.

4. Clinical issues. These center on the capabilities and limitations of doctors and other health-service providers, people identified with genetic conditions, and the general public in dealing with genetic information.

5. Effects on social institutions. Genetic tests reveal information about individuals and their families. Thus, test results can affect the dynamics within social institutions, particularly the family.

6. Conceptual and philosophical implications regarding human responsibility, free will vis-à-vis genetic determinism, and the concepts of health and disease.


Gene therapy


Main article: Gene therapy
Gene therapy using an Adenovirus vector. A new gene is inserted into an adenovirus vector, which is used to introduce the modified DNA into a human cell. If the treatment is successful, the new gene will make a functional protein.

Gene therapy may be used for treating, or even curing, genetic and acquired diseases like cancer and AIDS by using normal genes to supplement or replace defective genes or to bolster a normal function such as immunity. It can be used to target somatic (i.e., body) or germ (i.e., egg and sperm) cells. In somatic gene therapy, the genome of the recipient is changed, but this change is not passed along to the next generation. In contrast, in germline gene therapy, the egg and sperm cells of the parents are changed for the purpose of passing on the changes to their offspring.

There are basically two ways of implementing a gene therapy treatment:

1. Ex vivo, which means “outside the body” – Cells from the patient’s blood or bone marrow are removed and grown in the laboratory. They are then exposed to a virus carrying the desired gene. The virus enters the cells, and the desired gene becomes part of the DNA of the cells. The cells are allowed to grow in the laboratory before being returned to the patient by injection into a vein.

2. In vivo, which means “inside the body” – No cells are removed from the patient’s body. Instead, vectors are used to deliver the desired gene to cells in the patient’s body.

Currently, the use of gene therapy is limited. Somatic gene therapy is primarily at the experimental stage. Germline therapy is the subject of much discussion but it is not being actively investigated in larger animals and human beings.

As of June 2001, more than 500 clinical gene-therapy trials involving about 3,500 patients have been identified worldwide. Around 78% of these are in the United States, with Europe having 18%. These trials focus on various types of cancer, although other multigenic diseases are being studied as well. Recently, two children born with severe combined immunodeficiency disorder (“SCID”) were reported to have been cured after being given genetically engineered cells.

Gene therapy faces many obstacles before it can become a practical approach for treating disease. At least four of these obstacles are as follows:

1. Gene delivery tools. Genes are inserted into the body using gene carriers called vectors. The most common vectors now are viruses, which have evolved a way of encapsulating and delivering their genes to human cells in a pathogenic manner. Scientists manipulate the genome of the virus by removing the disease-causing genes and inserting the therapeutic genes. However, while viruses are effective, they can introduce problems like toxicity, immune and inflammatory responses, and gene control and targeting issues.

2. Limited knowledge of the functions of genes. Scientists currently know the functions of only a few genes. Hence, gene therapy can address only some genes that cause a particular disease. Worse, it is not known exactly whether genes have more than one function, which creates uncertainty as to whether replacing such genes is indeed desirable.

3. Multigene disorders and effect of environment. Most genetic disorders involve more than one gene. Moreover, most diseases involve the interaction of several genes and the environment. For example, many people with cancer not only inherit the disease gene for the disorder, but may have also failed to inherit specific tumor suppressor genes. Diet, exercise, smoking and other environmental factors may have also contributed to their disease.

4. High costs. Since gene therapy is relatively new and at an experimental stage, it is an expensive treatment to undertake. This explains why current studies are focused on illnesses commonly found in developed countries, where more people can afford to pay for treatment. It may take decades before developing countries can take advantage of this technology.


Human Genome Project

DNA Replication image from the Human Genome Project (HGP)

The Human Genome Project is an initiative of the U.S. Department of Energy (“DOE”) that aims to generate a high-quality reference sequence for the entire human genome and identify all the human genes.

The DOE and its predecessor agencies were assigned by the U.S. Congress to develop new energy resources and technologies and to pursue a deeper understanding of potential health and environmental risks posed by their production and use. In 1986, the DOE announced its Human Genome Initiative. Shortly thereafter, the DOE and National Institutes of Health developed a plan for a joint Human Genome Project (“HGP”), which officially began in 1990.

The HGP was originally planned to last 15 years. However, rapid technological advances and worldwide participation accelerated the completion date to 2003 (making it a 13 year project). Already it has enabled gene hunters to pinpoint genes associated with more than 30 disorders

KIDNEY Stone,Effects and Cure

                    KIDNEY Stone,Effects and Cure

• A kidney stone is a hard, crystalline mineral material formed within the kidney or urinary tract.
• Nephrolithiasis is the medical term for kidney stones.
• One in every 20 people develop kidney stones at some point in their life.
• Kidney stones form when there is a decrease in urine volume and/or an excess of stone-forming substances in the urine.
• Dehydration is a major risk factor for kidney stone formation.
• Symptoms of a kidney stone include flankpain (the pain can be quite severe) and blood in the urine (hematuria).
• People with certain medical conditions, such as gout, and those who take certain medications or supplements are at risk for kidney stones.
• Diet and hereditary factors are also related to stone formation.
• Diagnosis of kidney stones is best accomplished using anultrasound, IVP, or a CT scan.
• Most kidney stones will pass through the ureter to the bladder on their own with time.
• Treatment includes pain-control medications and, in some cases, medications to facilitate the passage of urine.
• If needed, lithotripsy or surgical techniques may be used for stones which do not pass through the ureter to the bladder on their own.

A kidney stone is a hard, crystalline mineral material formed within the kidney or urinary tract. Kidney stones are a common cause of blood in the urine (hematuria) and often severe pain in the abdomen, flank, or groin. Kidney stones are sometimes called renal calculi.

The condition of having kidney stones is termed nephrolithiasis. Having stones at any location in the urinary tract is referred to as urolithiasis, and the term ureterolithiasis is used to refer to stones located in the ureters.

Anyone may develop a kidney stone, but people with certain diseases and conditions (see below) or those who are taking certain medications are more susceptible to their development. Urinary tract stones are more common in men than in women. Most urinary stones develop in people 20-49 years of age, and those who are prone to multiple attacks of kidney stones usually develop their first stones during the second or third decade of life. People who have already had more than one kidney stone are prone to developing further stones.

In residents of industrialized countries, kidney stones are more common than stones in the bladder. The opposite is true for residents of developing areas of the world, where bladder stones are the most common. This difference is believed to be related to dietary factors. People who live in the southern or southwestern regions of the U.S. have a higher rate of kidney stone formation than those living in other areas. Over the last few decades, the percentage of people with kidney stones in the U.S. has been increasing, most likely related to the obesity epidemic.

A family history of kidney stones is also a risk factor for developing kidney stones. Kidney stones are more common in Asians and Caucasians than in Native Americans, Africans, or African Americans.

Uric acid kidney stones are more common in people with chronically elevated uric acid levels in their blood (hyperuricemia).

A small number of pregnant women develop kidney stones, and there is some evidence that pregnancy-related changes may increase the risk of stone formation. Factors that may contribute to stone formation during pregnancy include a slowing of the passage of urine due to increasedprogesterone levels and diminished fluid intake due to a decreasing bladder capacity from the enlarging uterus. Healthy pregnant women also have a mild increase in their urinary calcium excretion. However, it remains unclear whether the changes of pregnancy are directly responsible for kidney stone formation or if these women have another underlying factor that predisposes them to kidney stone formation.

Kidney stones form when there is a decrease in urine volume and/or an excess of stone-forming substances in the urine. The most common type of kidney stone contains calcium in combination with either oxalate or phosphate. A majority of kidney stones are calcium stones. Other chemical compounds that can form stones in the urinary tract include uric acid, magnesium ammonium phosphate (which forms struvite stones; see below), and the amino acidcysteine.

Dehydration from reduced fluid intake or strenuous exercise without adequate fluid replacement increases the risk of kidney stones. Obstruction to the flow of urine can also lead to stone formation. In this regard, climate may be a risk factor for kidney stone development, since residents of hot and dry areas are more likely to become dehydrated and susceptible to stone formation.

Kidney stones can also result from infection in the urinary tract; these are known as struvite or infection stones. Metabolic abnormalities, including inherited disorders of metabolism, can alter the composition of the urine and increase an individual's risk of stone formation.

A number of different medical conditions can lead to an increased risk for developing kidney stones:

• Gout results in chronically increased amount of uric acid in the blood and urine and can lead to the formation of uric acid stones.
• Hypercalciuria (high calcium in the urine), another inherited condition, causes stones in more than half of cases. In this condition, too much calcium is absorbed from food and excreted into the urine, where it may form calcium phosphate or calcium oxalate stones.
• Other conditions associated with an increased risk of kidney stones includehyperparathyroidism, kidney diseases such as renal tubular acidosis, and other inherited metabolic conditions, including cystinuria andhyperoxaluria.
• Chronic diseases such as diabetes andhigh blood pressure (hypertension) are also associated with an increased risk of developing kidney stones.
• People with inflammatory bowel disease are also more likely to develop kidney stones.
• Those who have undergone intestinal bypass or ostomy surgeryare also at increased risk for kidney stones.
• Some medications also raise the risk of kidney stones. These medications include some diuretics, calcium-containing antacids, and the protease inhibitor indinavir (Crixivan), a drug used to treat HIVinfection.
• Dietary factors and practices may increase the risk of stone formation in susceptible individuals. In particular, inadequate fluid intake predisposes to dehydration, which is a major risk factor for stone formation. Other dietary practices that may increase an individual's risk of forming kidney stones include a high intake of animal protein, a high-salt diet, excessive sugar consumption, excessive vitamin D supplementation, and excessive intake of oxalate-containing foods such as spinach. Interestingly, low levels of dietary calcium intake may alter the calcium-oxalate balance and result in the increased excretion of oxalate and a propensity to form oxalate stones.
• Hyperoxaluria as an inherited condition is uncommon and is known as primary hyperoxaluria. The elevated levels of oxalate in the urine increase the risk of stone formation. Primary hyperoxaluria is much less common than hyperoxaluria due to dietary factors as mentioned above.

While some kidney stones may not produce symptoms (known as "silent" stones), people who have kidney stones often report the sudden onset of excruciating, cramping pain in their low back and/or side, groin, or abdomen. Changes in body position do not relieve this pain. The abdominal, groin, and/or back pain typically waxes and wanes in severity, characteristic of colicky pain (the pain is sometimes referred to as renal colic). It may be so severe that it is often accompanied by nausea and vomiting. The pain has been described by many as the worst pain of their lives, even worse than the pain of childbirth or broken bones. Kidney stones also characteristically cause bloody urine. If infection is present in the urinary tract along with the stones, there may be fever and chills. Sometimes, symptoms such as difficulty urinating, urinary urgency, penile pain, or testicular pain may occur due to kidney stones.

How are kidney stones diagnosed?

The diagnosis of kidney stones is suspected when the typical pattern of symptoms is noted and when other possible causes of the abdominal or flank pain are excluded. Which is the ideal test to diagnose kidney stones is controversial. Imaging tests are usually done to confirm the diagnosis. Many patients who go to the emergency room will have a non-contrast CT scan done. This can be done rapidly and will help rule out other causes for flank or abdominal pain. However, a CT scan exposes patients to significant radiation, and recently, ultrasound in combination with plain abdominal X-rays have been shown to be effective in diagnosing kidney stones.

In pregnant women or those who should avoid radiation exposure, an ultrasound examination may be done to help establish the diagnosis.

Most kidney stones eventually pass through the urinary tract on their own within 48 hours, with ample fluid intake. Ketorolac (Toradol), an injectable anti-inflammatory drug, and narcotics may be used for pain control when over-the-counter pain control medications are not effective. Toradol, aspirin, and NSAIDs must be avoided if lithotripsy is to be done because of the increased risk of bleeding. Intravenous pain medications can be given when nausea andvomiting are present.

Although there are no proven home remedies to dissolve kidney stones, home treatment may be considered for patients who have a known history of kidney stones. Since most kidney stones, given time, will pass through the ureter to the bladder on their own, treatment is directed toward control of symptoms. Home care in this case includes the consumption of plenty of fluids. Acetaminophen (Tylenol) may be used as pain medication if there is no contraindication to its use. If further pain medication is needed, stronger narcotic pain medications may be recommended.

There are several factors which influence the ability to pass a stone. These include the size of the person, prior stone passage, prostate enlargement, pregnancy, and the size of the stone. A 4 mm stone has an 80% chance of passage while a 5 mm stone has a 20% chance. Stones larger than 9 mm-10 mm rarely pass without specific treatment.

Some medications have been used to increase the passage rates of kidney stones. These include calcium channel blockers such asnifedipine (Adalat, Procardia, Afeditab, Nifediac) and alpha blockers such as tamsulosin (Flomax). These drugs may be prescribed to some people who have stones that do not rapidly pass through the urinary tract.

For kidney stones that do not pass on their own, a procedure called lithotripsy is often used. In this procedure, shock waves are used to break up a large stone into smaller pieces that can then pass through the urinary system.

Surgical techniques have also been developed to remove kidney stones when other treatment methods are not effective. This may be done through a small incision in the skin (percutaneous nephrolithotomy) or through an instrument known as an ureteroscope passed through the urethra and bladder up into the ureter.

Rather than having to undergo treatment, it is best to avoid kidney stones in the first place when possible. It can be especially helpful to drink more water, since low fluid intake and dehydration are major risk factors for kidney stone formation.

Depending on the cause of the kidney stones and an individual's medical history, changes in the diet or medications are sometimes recommended to decrease the likelihood of developing further kidney stones. If one has passed a stone, it can be particularly helpful to have it analyzed in a laboratory to determine the precise type of stone so specific preventionmeasures can be considered.

People who have a tendency to form calcium oxalate kidney stones may be advised to limit their consumption of foods high in oxalate, such as spinach, rhubarb, Swiss chard, beets, wheat germ, and peanuts. Also drinking lemon juice or lemonade may be helpful in preventing kidney stones.

What is the prognosis for kidney stones?

Most kidney stones will pass on their own, and successful treatments have been developed to remove larger stones or stones that do not pass. People who have had a kidney stone remain at risk for future stones throughout their lives.

Behavior

                            Behavior 


Behavior is action that alters the relationship between an organism and its environment.
Behavior may occur as a result of

• an external stimulus (e.g., sight of a predator)
• internal stimulus (e.g., hunger)
• or, more often, a mixture of the two (e.g., mating behavior)

It is often useful to distinguish between

• innate behavior = behavior determined by the "hard-wiring" of the nervous system. It is usually inflexible, a given stimulus triggering a given response. A salamander raised away from water until long after its siblings begin swimming successfully will swim every bit as well as they the very first time it is placed in the water. Clearly this rather elaborate response is "built in" in the species and not something that must be acquired by practice.
• learned behavior = behavior that is more or less permanently altered as a result of the experience of the individual organism (e.g., learning to play baseball well).

Examples of innate behavior:

• taxes
• reflexes
• instincts

Reflexes

The Withdrawal Reflex

When you touch a hot object, you quickly pull you hand away using the withdrawal reflex.These are the steps:

• The stimulus is detected by receptors in the skin.
• These initiate nerve impulses in sensory neurons leading from the receptors to the spinal cord.
• The impulses travel into the spinal cord where the sensory nerve terminals synapse with interneurons.
• Some of these synapse with motor neurons that travel out from the spinal cord entering mixed nerves that lead to the flexors that withdraw your hand.
• Others synapse with inhibitory interneurons that suppress any motor output to extensors whose contraction would interfere with the withdrawal reflex.

Instincts

Instincts are complex behavior patterns which, like reflexes, are

• inborn
• rather inflexible
• valuable at adapting the animal to its environment

They differ from reflexes in their complexity.The entire body participates in instinctive behavior, and an elaborate series of actions may be involved.
The scratching behavior of a dog and a European bullfinch, shown here, is part of their genetic heritage. The widespread behavior of scratching with a hind limb crossed over a forelimb in common to most birds, reptiles, and mammals. (Drawing courtesy of Rudolf Freund and Scientific American, 1958.)
So instincts are inherited just as the structure of tissues and organs is. Another example.

• The African peach-faced lovebird carries nesting materials to the nesting site by tucking them in its feathers.
• Its close relative, the Fischer's lovebird, uses its beak to transport nesting materials.
• The two species can hybridize. When they do so, the offspring succeed only in carrying nesting material in their beaks. Nevertheless, they invariably go through the motions of trying to tuck the materials in their feathers first.

Interaction of Internal and External Stimuli

Instinctive behavior often depends on conditions in the internal environment.In many vertebrates courtship and mating behavior will not occur unless sex hormones (estrogens in females, androgens in males) are present in the blood.
The target organ is a small region of the hypothalamus. When stimulated by sex hormones in its blood supply, the hypothalamus initiates the activities leading to mating.
The level of sex hormones is, in turn, regulated by the activity of the anterior lobe of the pituitary gland.
The drawing outlines the interactions of external and internal stimuli that lead an animal, such as a rabbit, to see a sexual partner and mate with it.

Releasers of Instinctive Behavior

So once the body is prepared for certain types of instinctive behavior, an external stimulus may be needed to initiate the response. N. Tinbergen (who shared the 1973 Nobel Prize with Konrad Lorenz and Karl von Frisch) showed that the stimulus need not necessarily be appropriate to be effective.

• During the breeding season, the female three-spined stickleback normally follows the red-bellied male (a in the figure) to the nest that he has prepared.
• He guides her into the nest (b) and then
• prods the base of her tail (c).
• She then lays eggs in the nest.
• After doing so, the male drives her from the nest, enters it himself, and fertilizes the eggs (d).
• Although this is the normal pattern, the female will follow almost any small red object to the nest, and
• once within the nest, neither the male nor any other red object need be present.
• Any object touching her near the base of her tail will cause her to release her eggs.

It is as though she were primed internally for each item of behavior and needed only one specific signal to release the behavior pattern.
For this reason, signals that trigger instinctive acts are called releasers. Once a particular response is released, it usually runs to completion even though the stimulus has been removed. One or two prods at the base of her tail will release the entire sequence of muscular actions involved in liberating her eggs.
Chemical signals (e.g., pheromones) serve as important releasers for the social insects: ants, bees, and termites. Many of these animals emit several different pheromones which elicit, for example, alarm behavior, mating behavior, and foraging behavior in other members of their species.
The studies of Tinbergen and others have shown that animals can often be induced to respond to inappropriate releasers. For example, a male robin defending its territory will repeatedly attack a simple clump of red feathers instead of a stuffed robin that lacks the red breast of the males.
Although such behavior seems inappropriate to our eyes, it reveals a crucial feature of all animal behavior: animals respond selectively to certain aspects of the total sensory input they receive. Animals spend their lives bombarded by a myriad of sights, sounds, odors, etc. But their nervous system filters this mass of sensory data, and they respond only to those aspects that the evolutionary history of the species has proved to be significant for survival.

DNA as hereditary Material

                     DNA as hereditary Material
Griffith experiment:The evidences of hereditary nature of DNA was provided by British Microbiologist Fredrick Griffith.

• Types of bacteria used by Griffith:

1:S-type bacteria:The normal pathogenic form of this bacterium is referred as S-type bacterium or normal or wild type because it form smooth colonies on culture dish and contain POLYSACcHaRIDE coat.

2:R-type bacteria:The mutant form which lack the enzyme needed for the manufacture of polysaccharide coat,it is called mutant/R-type because it form rough colonies.

Experiment number 1:

• Griffith infected the mice with virulent strain S-type of streptococcus pneumoniae  bacteria,the mice died of blood poisoning.
• However when he infected the similar mice with mutant strain R-type of Pneumococcus that lack the plysaccharide coat.
• The mice show no illness
• The coat was apparently necessary for virulence.

Experiment number 2:

• To determine whether the plysaccharide coat had itself toxic substance or not?
• Griffith injected dead bacteria of virulent form S strain into ice the mice remain perfectly healthy.
• As a control he injected the mixture of dead S and live R or coatless bacteria.
• Unexpectedly the mice developed the disease and died of blood poisoning.

Conclusion:The blood of died mice was found high level of live virulent strains of S-type bacteria that was impossible.

Somehow information shows that coat was genetically transferred from Virulent S to Coatless R bacteria,this activity was not possible that the bacteria contain coat were dead.then how it was trasferred?

Three scientists, Oswald Avery, Colin MacLeod, and Maclyn McCarty, managed to show that Frederick Griffith’s transforming factor was in fact DNA, i.e. DNA is the heritable substance.

At first, Avery refused to believe Griffith’s results that actually challenged his own research on pneumococcal capsules - how could a rough capsule be converted into a smooth one? However, he soon confirmed Griffith’s results and set about trying to purify this mysterious “transforming principle” - a substance that could cause a heritable change of bacterial cells.

They extracted from Streptococcus pneumoniae S (containing a capsule) bacteria purified DNA, proteins and other materials and mixed R bacteria (lacking a capsule) with these different materials, and only those mixed with DNA were transformed into S bacteria. Therefore, DNA is the “transforming factor” and not proteins or other materials.

Amazingly, not everyone was convinced by the experiments of Avery's, MacLeod's and McCarty's as it was still widely assumed that genetic information was carried in protein. Firstly, due to Levene's influential "tetranucleotide hypothesis", many condsidered DNA to be a “stupid molecule,” made up of a repeat of the four chemical bases without any variations. Secondly, few biologists thought that genetics could be applied to bacteria, since they lacked chromosomes and sexual reproduction. Although the experimental findings of their experiment were quickly and independently a number of scientists still considered that protein contaminants were responsible the results. It was not be until the experiments of Hershey and Chase (1952) that DNA was finally proved and accepted to be the genetic material.

Hershey and Chase experiment

Historical background

In the early twentieth century, biologists thought that proteins carried genetic information.This was based on the belief that proteins were more complex than DNA.Phoebus Levene's influential "tetranucleotide hypothesis", which incorrectly proposed that DNA was a repeating set of identical nucleotides, supported this conclusion.The results of theAvery–MacLeod–McCarty experiment, published in 1944, suggested that DNA was the genetic material, but there was still some hesitation within the general scientific community to accept this, which set the stage for the Hershey–Chase experiment.

Hershey and Chase, along with others who had done related experiments, confirmed that DNA was the biomolecule that carried genetic information. Before that, Oswald Avery,Colin MacLeod, and Maclyn McCarty had shown that DNA led to the transformation of one strain of Streptococcus pneumoniae to another that was more virulent. The results of these experiments provided evidence that DNA was the biomolecule that carried genetic information.

Methods and results

Structural overview of T2 phage

Hershey and Chase needed to be able to examine different parts of the phages they were studying separately, so they needed to isolate the phage subsections. Viruses were known to be composed of a protein shell and DNA, so they chose to uniquely label each with a different elemental isotope. This allowed each to be observed and analyzed separately. Since phosphorus is contained in DNA but not amino acids, radioactive phosphorus-32 was used to label the DNA contained in the T2 phage. Radioactive sulfur-35 was used to label the protein sections of the T2 phage, because sulfur is contained in amino acids but not DNA.

Hershey and Chase inserted the radioactive elements into the bacteriophages by adding the isotopes to separate media within which bacteria were allowed to grow for 4 hours before bacteriophage introduction. When the bacteriophages infected the bacteria, the progenycontained the radioactive isotopes in their structures. This procedure was performed once for the sulfur-labeled phages and once for phosphorus-labeled phages.The labeled progeny were then allowed to infect unlabeled bacteria. The phage coats remained on the outside of the bacteria, while genetic material entered. Centrifugation allowed for the separation of the phage coats from the bacteria. These bacteria were lysed to release phage progeny. The progeny of the phages that were originally labeled with ³²P remained labeled, while the progeny of the phages originally labeled with ³⁵S were unlabeled. Thus, the Hershey–Chase experiment helped confirm that DNA, not protein, is the genetic material.

Hershey and Chase showed that the introduction of deoxyribonuclease (referred to as DNase), an enzyme that breaks down DNA, into a solution containing the labeled bacteriophages did not introduce any ³²P into the solution. This demonstrated that the phage is resistant to the enzyme while intact. Additionally, they were able to plasmolyze the bacteriophages so that they went into osmotic shock, which effectively created a solution containing most of the ³²P and a heavier solution containing structures called “ghosts” that contained the ³⁵S and the protein coat of the virus. It was found that these “ghosts” could adsorb to bacteria that were susceptible to T2, although they contained no DNA and were simply the remains of the original bacterial capsule. They concluded that the protein protected the DNA from DNAse, but that once the two were separated and the phage was inactivated, the DNAse could hydrolyze the phage DNA.

Experiment and conclusions

Hershey and Chase were also able to prove that the DNA from the phage is inserted into the bacteria shortly after the virus attaches to its host. Using a high speed blender they were able to force the bacteriophages from the bacterial cells after adsorption. The lack of ³²P labeled DNA remaining in the solution after the bacteriophages had been allowed to adsorb to the bacteria showed that the phage DNA was transferred into the bacterial cell. The presence of almost all the radioactive ³⁵S in the solution showed that the protein coat that protects the DNA before adsorption stayed outside the cell.

Hershey and Chase concluded that DNA, not protein, was the genetic material. They determined that a protective protein coat was formed around the bacteriophage, but that the internal DNA is what conferred its ability to produce progeny inside a bacteria. They showed that, in growth, protein has no function, while DNA has some function. They determined this from the amount of radioactive material remaining outside of the cell. Only 20% of the ³²P remained outside the cell, demonstrating that it was incorporated with DNA in the cell's genetic material. All of the ³⁵S in the protein coats remained outside the cell, showing it was not incorporated into the cell, and that protein is not the genetic material.

Hershey and Chase's experiment concluded that little sulfur containing material entered the bacterial cell. However no specific conclusions can be made regarding whether material that is sulfur-free enters the bacterial cell after phage adsorption. Further research was necessary to conclude that it was solely bacteriophages' DNA that entered the cell and not a combination of protein and DNA where the protein did not contain any sulfur.

Discussion

Confirmation

Hershey and Chase concluded that protein was likely not to be the hereditary genetic material. However, they did not make any conclusions regarding the specific function of DNA as hereditary material, and only said that it must have some undefined role.

Confirmation and clarity came a year later in 1953, when James D. Watson and Francis Crick correctly hypothesized, in their journal article "Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid", the double helix structure of DNA, and suggested the copying mechanism by which DNA functions as hereditary material. Furthermore, Watson and Crick suggested that DNA, the genetic material, is responsible for the synthesis of the thousands of proteins found in cells. They had made this proposal based on the structural similarity that exists between the two macromolecules, that is, both protein and DNA are linear sequences of amino acids and nucleotides respectively.

Other experiments

Once the Hershey–Chase experiment was published, the scientific community generally acknowledged that DNA was the genetic code material. This discovery led to a more detailed investigation of DNA to determine its composition as well as its 3D structure. Using X-ray crystallography, the structure of DNA was discovered by James Watson and Francis Crick with the help of previously documented experimental evidence by Maurice Wilkins and Rosalind Franklin. Knowledge of the structure of DNA led scientists to examine the nature of genetic coding and, in turn, understand the process of protein synthesis. George Gamow proposed that the genetic code was composed of sequences of three DNA base pairs known as triplets or codons which represent one of the twenty amino acids. Genetic coding helped researchers to understand the mechanism of gene expression, the process by which information from a gene is used in protein synthesis. Since then, much research has been conducted to modulate steps in the gene expression process. These steps include transcription, RNA splicing, translation, and post-translational modification which are used to control the chemical and structural nature of proteins.Moreover, genetic engineering gives engineers the ability to directly manipulate the genetic materials of organisms using recombinant DNA techniques. The first recombinant DNA molecule was created by Paul Berg in 1972 when he combined DNA from the monkey virus SV40 with that of the lambda virus.

Experiments on hereditary material during the time of the Hershey-Chase Experiment often used bacteriophages as a model organism. Bacteriophages lend themselves to experiments on hereditary material because they incorporate their genetic material into their host cell's genetic material (making them useful tools), they multiply quickly, and they are easily collected by researchers.