A researcher is studying gene expression in different types of cells. For a gene of interest, he notes its expression no longer appears to be regulated—it occurs in all cells, rather than in just a few cell types. The gene’s corresponding transcript and protein, however, appear normal. This may be the result of a mutation in which of the following regions associated with the gene? (5 POINTS)

Silencer

Intron

Exon

Promoter

9What role does the MutL protein play in DNA repair? (5 POINTS)

It performs a proofreading function, similar to DNA polymerase, and removes incorrect bases from the template DNA strand.

It recognizes and binds to a pair of "mismatched" nucleotides, preventing their translation.

It recognizes the newly-synthesized DNA strand (e. g., by detecting nicks), ensuring only it—and not the template strand—is repaired.

It helps to link together regions of DNA, after an error has been removed via exonuclease.

10If a mutation occurs that affects the large subunit of a ribosome, rendering it inactive, how would this affect translation? (5 POINTS)

The small subunit of the ribosome would fail to associate with a mRNA.

Methionine tRNA would not recognize the start codon of a mRNA.

New amino acids would not be added after the initial methionine, so translation would be effectively inhibited.

Arginine tRNA, rather than methionine tRNA, would associate with a mRNA’s stop codon.