People have been wondering why they look like their parents for centuries. Observations of nature over the past few millenia have led people to ask "Why?" and "How?" repeatedly. The search for answers has led to fascinating findings.
Genetic pioneering
Mendel's pea plant experiments jumpstarted the field of modern genetics. Once it was known that heredity was based in the cells and that genes carried the hereditary information, scientists built upon each other's work, adding more and more knowledge to the base.
Tiny animals that didn't take up too much laboratory space, didn't eat much, and that could create successive generations quickly were used to try out theories and learn more. Fruit flies (the genus and species name is Drosophila melanogaster) and mice or rats are most often used. To produce a new generation, which is the only way to see whether a mutation or trait is passed on, you must wait for the parental generation to mature to the point where they can reproduce. Then, you must wait through the gestation period once the parents have mated. Mice and fruit flies mature quickly and have short gestation periods. Humans, though, are not capable of reproducing until after puberty occurs during the teenage years, and then the gestation period is nine months. That's quite a wait for results!
Since Mendel's days in the monastery garden, DNA was found, and its structure was figured out. When James Watson and Francis Crick figured out that DNA was a double helix, scientists were able to determine that it split apart to be replicated. Once scientists knew how DNA was copied within the cell, they could figure out the genetic code. Knowing the genetic code allowed them to determine what amino acids and proteins were produced. And that led them to the Human Genome Project.
Mapping ourselves: The Human Genome Project
You've probably heard about this project on the news, even if you didn't know what a genome was at the time. (By the way, a genome is the total collection of genes in a species.) In 1988, laboratories all across the world began determining the DNA sequences of human DNA.
If you are wondering why the Human Genome Project is a big deal, think of it this way. If you were a researcher and you wanted to study a specific human gene, first you would have to know what chromosome it "lived" on. To provide the "address" of each human gene, researchers set out to build a map of the nucleotide sequences in the DNA of each human chromosome.
Sounds like a daunting task, doesn't it? Well, the process of DNA sequencing became automated, and with several laboratories around the country all working toward the same goal and sequencing different pieces of DNA using really sophisticated computer programs, the project was largely completed several years ahead of schedule — how often does that happen?
Now armed with a roadmap of where every gene is located, researchers can turn their attention toward making good use of that information. Knowing where each gene resides in the chromosomes, the "bad" genes — the ones that cause disease or cancer or other undesirable traits — can be sought out. Gene therapy research is trying to prevent the bad genes from having their undesirable effect or to convert them to good genes. It is predicted that the future of medicine will heavily use gene therapy to prevent the occurrence of diseases rather than medicines to treat diseases that have already taken hold.
However, now that research is dealing with human genes, plenty of controversy is peppering the positive results. An uproar in the 1980s occurred when a genetically engineered strawberry was created. As geneticists, biochemists, and molecular cell biologists discover more about what can be done with genetic information, others are worried about the implications of such technology. Even after gene therapy has been successfully used, people just are not sure how to approach the future.
Should gene therapy and cloning be regulated by the government? What would happen if genes being inserted into a patient went to the wrong chromosome? If plants and animals are altered, will the balance of nature be disrupted? Will "designer" babies be created? What do you call your mother if she's your clone, and therefore also your twin sister? These questions have been asked not only by researchers, but also by government officials, journalists, and people sitting around their dining room tables. But, with so much promise in developing genetic techniques, it is hard to contain enthusiasm. Researchers know that they can help people now. Why wait?
Table 1 gives you just a few examples of what is being done now with genetically engineered products. Table 2 shows you what is on the laboratory benches now. But before you know it, these tables will grow much longer. Any takers?
Table 1: Genetically Engineered Products
Product | Benefit |
Alpha-interferon | Normally produced in small amounts in the body, has very important immune function. Genetically engineered bacteria can cause the body to create lots of alpha-interferon. Now used to shrink tumors, as well as treat hepatitis B and hepatitis C. |
Beta-interferon | Also a naturally occurring protective protein that is produced in small quantities. The genetically engineered variety is used to treat multiple sclerosis, a serious autoimmune disorder in which the body attacks its own nerve fibers, eventually causing an inability to move. |
Humulin (human insulin) | In the past, pigs were used to create insulin that was used in humans with diabetes. However, because it was pig insulin, and not human insulin, some serious side effects could occur. Now, Escherichia coli, a very common intestinal bacteria, can be inserted with the gene for human insulin and turned into little human insulin factories. The insulin they make causes much fewer side effects and is much safer. |
Monoclonal antibodies | Antibodies are cells in the immune system that fight off invading organisms. Monoclonal antibodies are made by combining B lymphocytes (cells from the immune system) from mice with cancer-causing cells. These hybrid (mixed) cells start to produce antibodies against the cancerous cells. Monoclonal antibodies are used instead of chemotherapy in patients with a form of bone cancer. |
Tissue plasminogen activator (tPA) | This protein is the body's clot buster. It occurs naturally in the body to keep blood flow moving. What scientists did was genetically engineer the substance so that it could be produced outside of the body and in larger quantities. The genetically engineered product is given to patients who just had a heart attack or stroke to dissolve blockage that was the culprit. |
Table 2: Genetics in the Works
Product/Research Area | Expected Effect |
Functional genomics | Study of certain DNA sequences in an organism and how they function, taking into consideration all the DNA of the organism. |
Microarray analysis | Instead of studying one gene in one organism, the techniques associated with microarray analysis may allow thousands of genes to be studied at one time or in many different organisms at once. |
Antisense therapy | Hopes to stop bad genes from functioning, which would prevent the protein they produce from having a negative effect. |
Creating new chromosomes | Could possibly create entire human chromosomes that would contain genes to cure certain diseases. These could be inserted into people with a disease so that their body would replicate the good genes instead of the bad ones. |