Deck 9: Introduction to Genetic Diseases

Question 1

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?

A)Glutamate to aspartate.
B)Glutamate to proline.
C)Glutamate to isoleucine.
D)Glutamate to methionine.
E)Glutamate to tryptophan.

Answer 1

Glutamate to aspartate.

Question 2

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:

A)Sickle cell disease or α-thalassemia but not β-thalassemia.
B)α-Thalassemia but not sickle cell disease or β-thalassemia.
C)Sickle cell disease or β-thalassemia but not α-thalassemia.
D)Sickle cell disease but not α-thalassemia or β-thalassemia.
E)α-Thalassemia or β-thalassemia but not sickle cell disease.

Answer 2

α-Thalassemia but not sickle cell disease or β-thalassemia.

Question 3

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:

A)Indel.
B)Missense mutation.
C)Frameshift mutation.
D)Silent mutation.
E)Nonsense mutation.

Answer 3

Nonsense mutation.

Question 4

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?

A)During addition of a phosphate to a ribonucleoside.
B)During a visit to the beach with a lot of sunlight.
C)In a person suffering from Cockayne syndrome.
D)During addition of bases to a replicating DNA strand.
E)During the excision part of nucleotide excision repair.

Question 5

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?

A)AP endonuclease.
B)Topoisomerase II.
C)The 3'-exonuclease activity of DNA polymerase I.
D)A helicase that separates the strands.
E)An exonuclease that is part of the mismatch repair system.

Question 6

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?

A)You have cri-du-chat syndrome.
B)This is a benign condition, both for you and your future children.
C)You are probably phenotypically normal, but you can produce mentally retarded children
D)You are probably phenotypically normal, and your children will be at risk of mental retardation only if you produce them with a partner who has the same chromosome aberration.
E)This kind of abnormality is incompatible with life.

Question 7

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

A)Is more hydrophilic than hemoglobin A.
B)Is more hydrophobic than hemoglobin A.
C)Has a different number of electrical charges than hemoglobin A.
D)Has a more compact shape than hemoglobin A.
E)Has a different molecular weight than hemoglobin A.

Question 8

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

A)Deamination of bases in the DNA.
B)Formation of pyrimidine dimers.
C)DNA double-stranded breaks.
D)Alkylation reactions that modify the bases.
E)Depurination.

Question 9

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:

A)An exonuclease.
B)A DNA glycosylase.
C)AP endonuclease.
D)A topoisomerase.
E)A helicase.

Question 10

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:

A)Duchenne muscular dystrophy.
B)Cystic fibrosis.
C)-Thalassemia.
D)Sickle cell disease.
E)Huntington disease.