Exam 9: Introduction to Genetic Diseases

In every cell of the body, about 100 cytosine residues in the DNA are deaminated to uracil per day.The enzyme that recognizes this kind of damage and catalyzes the first reaction in the repair pathway is:

Most microsatellites have high mutation rates, and some become unstable once their length exceeds a certain limit.One example of a genetic disease that is caused by the expansion of a microsatellite in the affected gene is:

Spending a day on the beach is bad for your skin because sunlight causes:

A single-base substitution converts an A base in the coding strand of a gene into a T base, thereby changing the codon AAG, which codes for lysine, into UAG.This mutation is characterized as:

The loss of genes from the short arm of chromosome 5 is known to lead to the severe mental retardation of cri-du-chat syndrome.A chromosome painting probe reveals that you are missing most of the short arm of one copy of your chromosome 5, but this chromosome 5 material is found to be attached to the long arm of chromosome 10.What does this mean?

Some bases in the DNA can undergo spontaneous tautomeric shifts, forming chemical structures with unusual base-pairing properties.At what point is the presence of a tautomeric shift most likely to cause a mutation?

In sickle cell anemia, the replacement of glutamate by valine in position 6 of the β chain leads to serious trouble.Which of the following amino acid changes at position 6 would cause only a minimal change in the properties of hemoglobin?

Some abnormal bases that are produced by DNA-damaging chemicals can be removed by base excision repair.In this repair system, the initial removal of the abnormal base is followed up by which of the following enzymes?

Hemoglobin S can be separated from normal hemoglobin A by electrophoresis on paper or cellulose acetate foil.This is possible because hemoglobin S:

A girl had repeated attacks of pneumonia almost immediately after birth.A blood test taken 3 weeks after birth showed a blood hemoglobin concentration of 4.5% (normal at that age: 15% to 19%).This could possibly be a serious case of: