Dna 3 Essay, Research Paper
DNA – Deoxyribonucleic Acid – the material that codes for amino acids which form proteins, which in turn carry out functions of the cell. DNA is responsible for building life. Our physical characteristics, susceptibility to some diseases and disorders (e.g. breast cancer, sickle cell anemia), and a few behavior characteristics are passed from generation to generation through DNA. DNA controls everything about the way we look, from the color of the eyes to how tall you are to the width of your feet. Every person carries billions of copies of those DNA instructions. DNA is a molecule made up of smaller units. The basic unit of construction for the DNA molecule (DNA is considered a single molecule) is the base. There are four different bases found in deoxyribonucleic acid. These bases connect together into a long chain of bases to form the DNA molecule (much like pearls connect together to form a pearl necklace). The names of these four bases are adenine, cytosine, guanine, and thymine. Conventionally the bases are abbreviated as A, C, G, and T (respectively) for simplicity reasons. At the smallest level, DNA is organized into a double helix. The DNA helix is then repeatedly coiled to allow more of it to fit into a compact space. This helix replicates and passes on its information to the body’s cells.
In humans, all the DNA is packaged into 46 separate molecules called “chromosomes.” The chromosomes each contain thousands of genes, with each gene specifying how to make a particular protein necessary for cellular function. Scientists have long thought that the key to understanding human life lies in knowing the entire sequence of human DNA. Let’s take a look at some of the things that people are able to do with or to DNA, as well as the things still in the realm of science fiction. From a variety of applications of knowledge about DNA, I will talk only about three: Cloning, Genetic engineering and DNA Fingerprinting
I. Cloning
The idea of cloning has been considered since before the discovery of DNA. Cloning may give us insights into what makes us individuals, and how much of our personality and behavior is based on our genetics. It may also destroy our sense of individuality and the value of life.
A. History
It seems that every week, newspapers report on new advances in the science of cloning. Everybody knows about Dolly the cloned sheep, but few people know all the details about cloning, including the fact that scientists have been working on it for over 100 years.
1. Early Progress
The first cloned animals were created by Hans Dreisch in the late 1800’s. His original goal was not to create identical animals, but to prove that genetic material is not lost during cell division. Dreich’s experiments involved sea urchins, which he picked because they have large embryo cells, and grow independently of their mothers. Dreich took a 2-celled embryo of a sea urchin and shook it in a beaker full of seawater until the two cells separated. Eachgrew independently, and formed a separate, whole sea urchin. In 1902, another scientist, embryologist Hans Spemman, used a hair from his infant son as a knife to separate a 2-celled embryo of a salamander, which also grow externally. He later separated a single cell from a 16-celled embryo. In these experiments, both the large and the small embryos developed into identical adult salamanders. Spemman went on to propose what he called a “fantastical experiment” — to remove the genetic material from an adult cell, and use it to grow another adult. In this way, he theorized, he would be able to prove that no geneticmaterial was lost as cells grew and divided.
2. New Advances
There were no major advances in cloning until November of 1951, when a team of scientists in Philadelphia working at the lab of Robert Briggs cloned a frog embryo. This team did not simply break off a cell from an embryo, however. They took the nucleus out of a frog embryo cell and used it to replace the nucleus of an unfertilized frog egg cell, completing the “fantastical experiment” of nearly 50 years before. Once the egg cell detected that it had a full set of chromosomes, it began to divide and grow. This was the first time that this process, called nuclear transplant, was ever used, and it continues to be used today, although the method has changed slightly.
3. First Cloned Mammals
A breakthrough came in 1986. Two teams, working independently but using nearly the same method, each on the opposite side of the Atlantic, announced that they had cloned a mammal. One team was led by Steen Willadsen in England, which cloned a sheep’s embryo. The other team was led by Neal First in America, which cloned a cow’s embryo. Many advances were made during the course of these experiments, including progress in keeping tissue alive in lab conditions. However, neither team believed that it was possible to clone from an adult’s differentiated cells.
4. Dolly
Ian Wilmut at the Roslin Institute in Scotland was assigned to a project in 1986. His goal was to create a sheep that produced a certain chemical in its milk. He chose to alter adult cells, which held up well in laboratory conditions, and then clone them, producing animals with the altered gene all throughout their bodies. He began the paperwork in 1987, and began research in 1990. Wilmut’s team realized that differentiation did not matter in cloning. More work was done, and on July 5, 1996, a lamb was born, cloned from a frozen mammary cell from another adult sheep.
Although Dolly was just a step in a long experiment, the press descended upon the first animal cloned from an adult. The Roslin Institute was overrun with journalists and reporters. However, other scientists were critical — Dolly took 277 tries to create, and other labs were unable to reproduce the results. In addition, it took over a year for the institute to test Dolly’s DNA to make sure that it was indeed the same as that of the frozen mammary cells. Science, although temporarily impressed, demanded a better way.
5. Herd of Mice
Oct 3, 1997, the Honolulu Technique created Cumulina the cloned mouse. She was cloned from cumulus cells (cells which surround developing egg cells) using traditional nuclear transfer. The nucleus was taken from the cumulus cell and implanted in an egg cell from another mouse. The new cell was then treated with a chemical to make it grow and divide. The scientists repeated the process for three generations, yielding over fifty mice that are virtually identical by the end of July 1998. The Honolulu Technique’s success rate of 50:1 is almost six times better than that of the Roslin Institute’s success rate, 277:1. As cloning technology improves, more and more applications will be seen in everyday life.
6. Mainstream Cloning
How much do you love your dog? Is your dog so perfect that you would pay over $2.3 million dollars to have another just like it? One couple thinks their 11-year-old dog is just such an animal. Wishing to remain anonymous to avoid run-ins with the press, this couple has contracted Texas A&M University to clone their dog, Missy. Scientists are hailing this for its scientific achievement; no dogs have been cloned before because their reproductive system is rather complicated. If the cloning of dogs can be achieved, perhaps exceptional animals like rescue animals can be reproduced. In addition to the pure scientific appeal of cloning a dog, the attempt to clone Missy has another interesting addition to make to the history of cloning. A private couple wants their dog cloned. They are, of course, spending millions to have her cloned, but consider the possibilities. Could cloning the family pet one-day become a normal alternative to buying a new one?
B. Future of cloning
Cloning is truly a monumental accomplishment. But what can we do with it? Very few see a future society of cloned humans. Mad scientists with armies of cloned zombies are highly improbable due to the current cost, failure rate, and time involved. However, there are some practical applications currently being considered. Which are possible and which are doomed to remain in the realm of science fiction? Only the future will tell.
1. Farming
The average dairy cow puts out roughly 15,000 gallons of milk a year. However, there are certain, special cows that can make up to 45,000 gallons a year. Selectively breeding for this trait is nearly impossible given the complexity of the genetics governing milk production. However, if scientists clone these exceptional cows, the profit gained from increased milk outweighs the money spent on a cloned cow.
2. Infertility Treatment
While it is unlikely that the cloning of humans will ever become standard practice, it is also unlikely that it will never be attempted. Many people see cloning as a way to provide children for those couples who cannot have them naturally. While there is always someone willing and able to pay the price, is the cloning of humans morally right?
3. Jurassic Park
Scientists have told us that it would be virtually impossible to find an intact cell from an extinct dinosaur. However, at New Zealand’s University of Otago, scientists are trying to clone the extinct moa, once the world’s largest bird. The plan was to take DNA from its leg bone and implant it into a chicken egg to grow. The scientists were then going to breed the new moa with an ostrich or an emu to create a new giant bird. Research was stopped by the Ngai Tahu Maori tribe, which claims to own the DNA because they were sole owners of the land when the bird became extinct around 1500.
In 1992, a herd of cows that was damaging the ecological balance of New Zealand’s Enderby Island was almost completely destroyed. All that remained was the frozen sperm of ten bulls, and one living female, Lady. Because Lady is so old, all attempts to make her pregnant using the frozen sperm have failed. Therefore, Lady was cloned. On July 31, 1998, Elsie (L.C., Lady’s Clone) was delivered by Casarean section, is the hope of preserving the nearly extinct Enderby Island cows.
4. Organs for Transplant
Another option open to the future is the cloning of specific organs for transplant. Each year, many people die, unable to find a suitable organ donor. In addition, those who do find donors many times have to take anti-rejection drugs for the rest of their lives. If scientists can find a way to force cells to differentiate to become a failing organ, they should be able to grow those cells into a working, adult organ. Because the new organ would be an exact match for
the patient, there would be no need for anti-rejection drugs. Many predict that the first organ to be cloned in this way may be bone marrow, because it is a liquid organ and has no shape. However, it is conceivable that solid organs would be able to be cloned outside a body as well.
II. Genetic Engineering
A. History
If genetic engineering is defined as changing an organism’s DNA to make it more beneficial, genetic engineering has been going on for a very, very long time in the form of selective breeding. However, actually going into a cell and changing its genome(the complete set of DNA contained in an organism’s cell) by inserting or removing DNA is a very new technology.
1. Modern Genetic Engineering
Modern genetic engineering began in 1973 when Herbert Boyer and Stanley Cohen used enzymes to cut a bacteria plasmid (ring of “extra” DNA found outside the nucleus in many single-celled organisms)and insert another strand of DNA in the gap. Both bits of DNA were from the same type of bacteria, but this milestone, the invention of recombinant DNA technology, offered a window into the previously impossible — the mixing of traits between totally dissimilar organisms. To prove that this was possible, Cohen and Boyer used the same process to put a bit of frog DNA into bacteria.
In 1990, a young child with an extremely poor immune system received genetic therapy. Some of her white blood cells were genetically manipulated and re-introduced into her bloodstream. These new cells have taken over for the original, weak white cells, and her immune system now works properly. Although relatively few people have had their cells genetically altered, these advances have made the prospect of mainstream genetic medicine seem more likely.
2. Current Status
As of late summer of 1998, scientists are able to add simple traits to organisms. They cannot create custom-made animals. They cannot always predict how traits will interact. Before phenomenally new advances can be made, scientists have to learn how to affect cells’ DNA with pinpoint accuracy, without affecting other traits. Advances like genetic correction for nearsightedness are a long way off. The power of science is limited to knowledge about genetics, gene locations, and trait interactions, but as knowledge grows, so will scientists’ abilities to manipulate life. Genetic Engineering is, quite possibly, the most promising and most threatening new advance in medical technology of all time. For this reason, new advances made in the future may or may not be implemented. It is nearly impossible to predict what Genetic Engineering will bring to the future, but there is some speculation.
3. The Promise
Genetic engineers hope that with enough knowledge and experimentation, it will be possible in the future to create “made-to-order” organisms. This will lead to new innovations, possibly including custom bacteria to clean up chemical spills, or fruit trees that bear different kinds of fruit in different seasons. Any trait occurring in nature can theoretically be mixed with any other to form a totally new organism that would not otherwise occur in nature.
B. Possible applications:
1. Medicine
The most popular contribution of Genetic Engineering is in the field of medicine. Because most diseases have a genetic component, healing may be sped along in the future by using bacteria-made proteins to augment the healing process. Proteins circulate through the body, reporting to various glands whether bone and muscle mass should increase or decrease, how salty substances should be moved through the lungs, how many immune cells should be manufactured, and even how fast hair should grow. The genes regulating the production of these proteins can be inserted into bacteria, “teaching” the bacteria how to make the identical proteins.
Unfortunately, this is a power that is easily abused. Athletes could have their muscle mass increased for more strength. It could be that the army with the most genetic drugs coursing through their veins would be the one to win the war. Many people feel that these dangers far outweigh the good that could be done speeding the healing process.
2. Food
One controversial advance has been in place for several years: genetically engineered food. Dubbed “Frankenfoods” by opponents, these foods are enhanced by genes from other plants or animals. This can enhance nutrition, shelf life, or taste. Depending on public reaction, these foods may be widely available in the future.
III. DNA Fingerprinting
Like a fingerprint, a person’s DNA is virtually unique. It can be retrieved from blood, hair, skin, blood, saliva, semen and other bodily fluids and the pattern that is revealed when it is analyzed may be used to identify you, categorize you and control you. Ever since the famous OJ Simpson trial, DNA Fingerprinting has been in the news. DNA samples taken from blood at the crime scene were compared to samples from O.J. Simpson, Nicole Brown Simpson, and Ron Goldman. Prosecution witnesses have testified that the DNA tests link O.J. Simpson to the murders, while defense witnesses supports the claim that crime scene samples have been contaminated or could have been planted as part of a conspiracy against Simpson September 25, 1995 from ‘CNN Presents’ and Correspondent Art Harris.
The Simpson trial was billed as “High Noon” for DNA. Faced with two murders no witnesses, and no weapons, prosecutor were banking on blood to tell the story through DNA tests pointing to one man, damning O.J. Simpson with his genetic fingerprints. Detective Tom Lange of the Los Angeles Police Department, a lead investigator, described for jurors the scene of the crime: a river of blood, two bodies butchered beyond belief, and a curious trail of blood drops leading away from Nicole Brown Simpson’s condo to O.J. Simpson’s estate. They found blood on her back gate, blood in his driveway, blood in his front hall. And when they checked, they found blood in his white Bronco. Lab tests show the blood was O.J. Simpson’s. But blood matching O.J. Simpson wasn’t the only blood found in places hard to explain. Blood consistent with the two victims was on the telltale glove behind Simpson’s house and in his Ford Bronco. And blood matching his ex-wife’s was on socks on his bedroom floor. “That trail of blood from Bundy through his own Ford Bronco and into his house on Rockingham is devastating proof of his guilt.” said- Marcia Clark, Los Angeles County prosecutor. Scientists say blood doesn’t lie, and one prosecution expert told the jury blood drops near the victims had to be Simpson’s, that the blood could have come only from one person, black or white, out of 170 million. Facing those odds, the defense went after the people who handled the blood — police and lab technicians — in a double-barreled attack that evidence was ontaminated by bungling and a racist cop may have planted evidence to frame O.J. Simpson.
Scientists can take an intact cell and turn it into a conviction, a pardon, or a restored family. The odds are one in 70 billion (140 times Earth’s population) that the results are inaccurate. However, DNA fingerprinting is sometimes refutable evidence, even with such low odds of inaccuracy. If the technician confused the DNA samples or deliberately gave false results, the information gleaned from a DNA test would be useless. Also, DNA evidence only proves that a person was present. It does not prove that the depositor of the DNA was the actual criminal. For these reasons, there must be other evidence to support the DNA fingerprints’ conclusion; the fingerprints alone are not enough for a conviction.
Establishing Innocence
DNA Fingerprinting can help to speed along court cases by eliminating suspects. Between 1989 and 1996, the FBI used genetic testing in about 10,000 sexual assault cases; in 2,000 of those cases, the prime suspect was discovered to have not committed the crime. Without genetic testing, it can be assumed that some of these men would have been convicted. In fact, many prison inmates have appealed their conviction after spending years in jail, and have been discovered to be innocent.
Identification
As a result of the unidentified remains of American soldiers that have been found abroad, the U.S. military has been compiling data from mitochondrial DNA to help identify the soldiers. Mitochondrial DNA is passed on by the mother only, and as a result, remains mostly identical within families. By testing DNA from the bones of the remains of soldiers against the military’s database, scientists have identified 500 soldiers so far, and another 250 more are under study.
Human Genetics Concepts and Applications, Second Edition
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