The Human Genome Project

• ancient man used intuitive understanding of genetics to breed corn and animals
• Dr. Archibald Garrod (British) made two observations
  • recognized that diseases occurred in parents who were related
  • some human diseases were caused by a lack of chemical factors (enzymes)
• Morgan (at Columbia) began breeding Drosophila and found that males were XY and females were XX
• 1910-20 saw explosion in area of genetics; experiments and research done on mice, molds, fruit flies, and man
• population geneticists believe that if everything in man is genetically inherited, they must study humans
• 1944-5 people believed the hereditary material was protein and that DNA provided the structure for proteins
• Avery, et al. (1940's) experiments with rough and smooth pneumonia bacteria in rats showed that the malignancy of the bacteria was transferred through DNA
• 1952-4 Watson and Crick discovered the double helix structure of DNA
• scientists discovered that there were 46 chromosomes, rather than 48 as had been previously believed
• after the atomic bomb, many of the PhD's that had worked on the project now began to design a machine which would enable one to sort chromosomes
• 1965 in Baltimore, Dan Nathans questioned how bacteria survived when when invaded by foreign DNA; he used gel electrophoresis and found that the same gel pattern was created every time the same restriction enzymes were used to cut the DNA - restriction enzymes cut at specific sites
• 1972 in Honolulu, Boyer and Cohen came up with the idea of inserted foreign DNA into bacteria to make protein product for commercial use - the birth of the bioengineering industry

Turners Syndrome is a disease in which a female is born with only one Xchromosome. In normal females, every cell of the body, only one Xcell is actually activated and working, but somehow the presence of the other (inactive) Xis necessary for a normal functioning person. 90% of spontaneous abortions occur because of this type of chromosomal imbalance.

Kleinfelter's Syndrome is a disorder in which a man is born with XXY. The Ydetermines the sex of the man but the extra Xgives him a slight degree of feminization and usually some degree of mental retardation. An increase in criminality is seen among men with this disorder.

These two diseases provoked extensive research on human genetic diseases. The Scandanavian scientist Kasperon found that you could put an inhibitor into the cells to stop the cells at the point of mitosis - enabling the metaphase chromosomes to be isolated and studied. The chromosomes can be stained for identifying patterns and then matched on a chromosome map to look for major anatomical abnormalities.

Insulin is a small protein that regulates the sugar level in the blood. In 1977, it was predicted that there would not be enough insulin manufactured to treat all the diabetic people in the world. Eli Lilly controlled the production of insulin. Cohen and Boyer began to isolate the insulin gene. Bill Rutter of University of Cal. at San Fransisco tried to isolate the gene from chromosome 11, but could never get a constant restriction enzyme digestion pattern from the gel electrophoresis because next to the insulin gene on the DNA is an area which is highly polymorphic (multiple copies of a nucelotide triplet that differs in copy number from one individual to the next).

Sickle-cell Trait results from a change in an amino acid of beta-globin whereby a single base change causes a glutamic acid to be changed to valine. The mutant beta-globin aggregates into a large structure that crystalizes inside the red cell and becomes sickle shaped. This shape cell does not pass easily through capillaries, and creates major problems in the individual. The only successful treatment is constant blood transfusions (every 3 weeks) to keep the body from making its own faulty red cells in the bone marrow.

In 1975-6 at UC San Fransisco, Y.W. Kan worked with the globin gene by separating DNA with restriction enzymes and isolating the globin gene. Kan was able to diagnose sickle-cell trait in an unborn baby by withdrawing blood from the placenta, although this test caused an unintended abortion 1/3 of the time. Kan knew that if it were possible to test the baby's cells rather than the placenta, the fatality rate would be less than 1%. Kan took a family in which both the mother and father were sickle cell carriers and looked at the RFLPs to try to find correlations between the patterns. Kan was able to make the first molecular diagnosis of sickle cell by using RFLPs.

Wexler's mother died of Huntington's Disease, an illness in which a person around the age of 20-25 begans to experience behavior change and brain deterioration. The original mutation is thought to have occurred in a British sailor who then transferred the gene to a number of people in Columbia. 167 cases of HD were found in one area. Wexler took samples of the DNA of many of these people and used RFLPs to find markers on chromosome six that showed the presence of HD. The mutation is due to the fact that the HD gene has variable number of a repeated sequence within the gene. This repeat number is very unstable and the number of tandem repeats differs from individual to individual. The more repeats an individual has in the HD gene, the more severe the disease. This disease is dominant, but rare.

Dominant diseases usually involve problems of structure while most recessive diseases are caused by a lack of enzyme or a malfunctioning protein.

Predictive medicine raises many questions, some of which we've discussed in class. Such questions are:

• would you want to know if you were going to have a disease?
• What if the disease had no treatment?
• How far can law back up questions of testing?
• Who has the right to test a child?
• What rights do companies and employers have to know the results of your tests?

These questions are difficult to answer and no laws have yet been established to deal with these issues.