BRS Genetics

Question 1

What is the function of topoisomerase inhibitor etoposide?

Answer 1

Topoisomerase creates double-stranded breaks ahead of the replication fork to relieve the supercoiling induced by the action of helicase.

Question 2

Certain nucleoside analogs inhibit DNA synthesis because they lack which of the following properties required for normal DNA polymerization?

Answer 2

DNA polymerase requires a free 3’-hydroxyl group on deoxyribonucelotide, which acts a nucleophile to attacks the 5’-alpha-phosphate of the incoming nucleotide, which from the phosphodiester bond.

Question 3

Rifampin inhibits which one of the following types of enzymes?

A. DNA-dependent DNA polymerase

B. DNA-dependent RNA polymerase

C. RNA-dependent DNA polymerase

D. RNA-dependent RNA polymerase

Answer 3

B. Rifampin is an important agent in a multidrug regimen for tuberculosis; it inhibits the beta subunit of the DNA-dependent RNA polymerase (RNA polymerase).

Question 4

Quinolone antibiotics inhibit ____, a prokaryotic topisomerase.

Answer 4

DNA gyrase

Question 5

Which of the following statement best explains mtDNA?

A. Inherited equally from both parents

B. replicated with increased fidelity with respect to nuclear DNA

C. shares the same genetic code as nuclear DNA

D. double-stranded circular DNA

Answer 5

D

Question 6

Pseudouridine and ribothymidine are nucleotides in which type of nucleic acid?

A. tRNA

B. rRNA

C. hnRNA

D. mRNA

E. snRNP

Answer 6

A. tRNAs often contain post-transcriptionally modified bases, including the conversion of uridine to pseudouridine and ribothymidine.

Question 7

MERRF xpression is highly variable. Which explains the variable expression of this disease?

A. Variable expressivity

B. Incomplete penetrance

C. heteroplasmy

D. allelic heterogeneity

Answer 7

C. heteroplasmy

Question 8

Which is characteristic of the mitochondrial genome?

A. It has a low mutation rate

B. DNA is bound to histones

C. It has no introns

Answer 8

C

Question 9

In _______ heteroplasmy is rare and disease expression is relatively uniform.

Answer 9

Leber’s hereditary optic neuropathy (LHON)

Question 10

The incidence of neural tube defects is 1 in 200. What is the approximate recurrence risk for first-degree relatives?

Answer 10

D) 1 in 14

Risk of recurrence for first-degree relatives is approximately the square root of its incidence