Nowadays, scientists have learned a great deal about the chemical changes taking place inside living things. They have deciphered the code, DNA, by which animals and plants pass on their characteristics to their offspring. They have even leant how to alter that code to produce life forms with new characteristics. This new technology involving both chemical and biological science is known as genetic engineering. Through this new technology, we shall soon be able to provide much better treatments, and possibly even cures for certain serious diseases, especially those like inheriting diseases, which cannot presently be cured.
Besides, we shall be able to create new kinds of life, or altered version of existing animals and plants, for medical and industrial uses. Basic, Individual, Building Unit of Life All living things are built up by millions of millions of same fundamental working parts. These are called cells. Cells are microscopic, however there are many different kinds of cells with different properties for a particular task in a living things. For instances, a nerve cell is particularly used for carry messages to and from he brain and have a specific shape differs the others.
Nucleus, the most important part of a cell, which directs the making of essential substances, called proteins, on which all life depends. However, each different organism has its own specific kind of proteins. How do they know which kind of protein are essentials? Inside the nucleus of the cell of each organism, has a special, complex chemical called DNA (deoxyribonucleic acid). These DNA contains the instruction and informations of what kind of proteins have to be made. DNA is shaped like a twisted rope ladder.
The rungs of the ladder are made up of four chemical bases, which are adenine (A), thymine (T), guanine (G), and cytosine (C). Each of these bases has special shape that A can only attach with T and G can only attach with C. The sequences of how the bases arrange are the information of what proteins are made. A section of DNA that has the complete code for a single protein is called gene. That’s also what’s genetic engineering working on. Genes determine the type of proteins our bodies make. It controls a huge variety of factors that help make us unique individuals.
As this fact, nobody has exactly the same set of genes as you have, unless you have an identical twin, everyone is looks exactly like you. Genes are stored on long strands of DNA known as chromosomes inside the nuclei of our cells. Most of the cells in your body contain 46 chromosomes, arranged in 23 pairs. Each cell contains the complete set of DNA. Not every cell in the body uses every instruction on the DNA in its nucleus. Instead, it reads only those parts needed to manufacture certain proteins. Inheriting Disease Most of our cells contain 46 chromosomes.
However, two type of cells in human beings that have only half this number. These are the egg cells in females and the sperm cells in males. When fertilization takes place, a sperm joins with an egg, and the 23 chromosomes from each combine to make a new set of 46. That is, all genes in human come from two versions that are 23 chromosomes from your mother and 23 from you father. Although there is two version of the same type of gene, sometimes only one version is used, this gene is call dominant gene. The other is said to be recessive. Inherited diseases or genetic diseases are of two types.
The first are those resulting from a disease-causing dominant gene inherited from either the father or the mother. In this case, the parent who passes on the unhealthy gene must also be a sufferer of the disease. The second type appears when two recessive genes receive from both parents. Since there is no choice but for either one switched on. Huntington’s Disease One of the well-known genetic diseases is called Huntington’s Disease named after George Huntington, the doctor who first described it in 1872. This inherited disease affects about 30,000 people in the United States.
It causes depression, bursts of anger or violence, memory loss, confusion, and shaking movements that, as the disease advances, grow into a grotesque, writhing “dance” that never stops. All these effects result from destruction of small but vital areas of the brain called the basal ganglia, destruction masterminded by a single dominant gene. Huntington’s disease is one of about 4,000 human diseases had known to be inherited. There is no cure or even treatment for this relentless disease. Perhaps most tragic of all, signs of it usually do not appear until a person is 30 or 40 years old.
By then, many of its victims have had children. There is a 50-50 chance of passing it on to each offspring. Because the gene is dominant, anyone who inherits it will develop the disease. Scientists all over the world went through a several years of hard work to find where the disease-causing gene is located. It is significantly important to know where it located and discoveries how it produces certain proteins to distract the brain, in order to cure this disease. By this disease we can see how genetic engineering applies for medical uses. Nancy Wexler
If we talk about this disease, it is impossible not to mention about Nancy Wexler. When she was 23, she learned that her mother, Leonore, had Huntington’s disease. That means there is 50-50 chance that she has inherited the genetic mutation and will eventually die just as her mother finally did. “She went from being dismal to being challenged and wanting to be a knight in shining amour going out to fight the devils,” recalls her father, Milton Wexler. She didn’t devastated by the experience of her mother dying slowing by the disease that threatened her family, instead she is a fighter.
In 1969, Nancy Wexler became President of the Hereditary Disease Foundation, a clinic founded by her father. She received her doctor’s degree in 1974. She formed the Huntington’s Disease Collaborative Research Group, to hunt the location of the gene. She not only functioned as a scientist but as catalyst, keeping scientists from different nations doing the same research. Needle In A Genetic Haystack David Housman of the Massachusetts Institute of Technology (MIT) brought up an idea that the best thing they could do to combat Huntington’s would be to find the gene that caused it.
Such a discovery would produce a test for the disease, which would allow people to find out whether they carried the dangerous gene before they had children. It also could lead to a better understanding of the illness and, possibly, a treatment or even cure for it. Human has more than 100,000 genes, how can they find one gene among them? Housman suggested the use of restriction enzymes, the new technique developed by molecular biologists. Genes differ slightly in length and composition from person to person, a particular restriction enzyme did not snip everyone’s DNA into pieces of exactly the same size.
They called them restriction fragment length polymorphisms (RFLPs), pronounced “riflips”. Housman explained that RFLPs could be used as markers for other genes that were as yet unknown. If a particular form of RFLP was always or almost always inherited along with a certain gene, the gene was almost sure to lie very close to the RFLP on a chromosome. If there is procedure without materials, work cannot proceed. Nancy Wexler had known about the Venezuelan family. Venezuelan family is a big Huntington’s family on the shores of a large lake called Maracaibo. But the members of the family living in three different villages.
She returned to Venezuela to collect blood and skin samples members for DNA testing. In 1983, James Gusella, a graduate student of Housman’s, found a particular maker inherited with Huntington’s gene in Iowa, another big Huntington’s family. He then turned to Venezuela, and comparing both. He then certain that that the maker of Huntington’s gene. The most immediate result of Gusella’s discovery was the creation of a test that showed with about 6 percent certainty whether a person would develop Huntington’s disease. The test began to be used in 1986. But this sparked out a controversy ethics issues. Twilight Zone of Genetics
Although the maker of Huntington’s gene was found, but that’s not enough to develop a cure or treatment for the disease. Their next quest was to search for the Huntington’s gene itself. Despite the collaborative research group’s best efforts, the Huntington’s gene remained elusive throughout the 1980s. By 1984, the group had learned that the maker RELP, and therefore the disease gene, was on the short arm of chromosome 4. For many years the Huntington’s group thought their quarry was almost at the end of the chromosome arm, a region so difficult to analyze that Wexler had called it “the Twilight Zone of genetics.
Then, just as the end region was finally sequenced, evidence began suggesting that the gene be in fact farther in on the chromosome. The sequencing had to begin all over again. The group’s quest was finally successful early in 1993. Marcy MacDonald, a senior researcher working with James Gusella, was the one who sequenced the Huntington’s gene, and also learned what was wrong with it. Huntington’s Gene The Huntington’s gene that scientists search for many years was a sort of stutter, a repeating sequence of the bases C-A-G.
The genes of people unaffected by the disease had between 11 and 34 of these repeats. In people who developed Huntington’s, however, the repeats numbered 42 or more. Later, a research found out that the more repeats an affected person’s gene had the sooner in life the disease would appear and the more severe it would be. How Gene Leads to Huntington’s Four years after the discovery of the defective gene that causes Huntington’s disease, researchers have produced the first clues about how the gene causes the devastating disorder.
Scientists found that genetic diseases share the same defect with Huntington’s which a genetic “stutter” that inserts from 30 to 150 copies of the amino acid glutamine into key proteins, altering their properties and causing the disease. They now developing drugs for treatment which delay the onset of symptoms. Genetic Ethics Since the genetic screening can only be used to predict whether a person might develop a genetic disease. It gives probabilities, not certainties. However, as this becomes increasingly common, discrimination arises. For Huntington’s, if a person carried it, possibly he will not be hired.
But we can also take advantage of this technology. For instance, if a woman, who knows she has inherited a tendency to develop breast cancer, might decide to have frequent mammograms so that tumor can be detected while they are still small and easily removable. The Future The new techniques of genetic engineering will solve some important problems while at the same time creating others. Within 50 years, many of today’s most devastating illnesses may be not only treatable but also curable. If people use it in a right way, it will benefit us a lot. Or otherwise, may produce problems more than it be able to solve.