An E.coli strain contains a mutation in the malate dehydrogenase gene that results in a stop codon at amino acid position 14.From subcultures of this strain,a colony was obtained that was capable of making malate dehydrogenase.Your approach to examining this phenomenon should be to examine
A)the DNA sequence to see if a reversion has occurred.
B)the DNA sequence to see if a suppressor mutation has occurred.
C)other proteins to see if other stop codons are ignored,indicating the presence of a suppressor tRNA.
D)the DNA and plasmids for the incorporation of a second complete copy of the malate dehydrogenase gene.
E)All of these approaches need to be considered.

Question

Quizplus · Accepted Answer

All of these approaches are valid for examining how a colony has regained the ability to produce malate dehydrogenase despite the original mutation. A reversion could restore the original gene function (A), a suppressor mutation elsewhere could bypass the stop codon effect (B), a suppressor tRNA could allow read-through of stop codons (C), and the acquisition of a new copy of the gene could compensate for the mutated one (D).

An EColi Strain Contains a Mutation in the Malate Dehydrogenase Gene