A plant is homozygous for a point mutation in gene B.This plant produces wild-type B protein in wild-type amounts,but a more detailed analysis reveals that the B mRNA produced by this plant is two nucleotides shorter than wild type.The mutation is most likely a two base-pair deletion:
A)downstream of the STOP codon,in the last exon of gene B.
B)in an intron of gene B away from the splice sites.
C)in the open reading frame of gene B.
D)that removed a splice site of gene B.
E)within the promoter of gene B.

Question

Quizplus · Accepted Answer

The mutation is most likely a two base-pair deletion downstream of the STOP codon, in the last exon of gene B. This is because the mutation does not affect the amount of B protein produced, but it does affect the length of the B mRNA. This suggests that the mutation is in the 3' untranslated region (UTR) of the B mRNA, which is located downstream of the STOP codon.

A Plant Is Homozygous for a Point Mutation in Gene