Question

A mutation occurs in which a base (T) is inserted into the DNA sequence after the G, at the position marked with an asterisk, before transcription begins. How will this alteration influence the mRNA produced?

Answer 1

A mutation which occurs when a base is introduced into the DNA sequence before transcription begins will lead to frame-shift of a single base on the DNA sequence resulting in nonfunctional protein from the transcribed mRNA.

Explanation:

This change either through addition or deletion of a single base in the codon sequences of the DNA will modify the amino acid codes and will result in nonfunctional proteins after transcription.

This mutation will just result in change of a single base, i.e., it would be added either to the enhancer region or the silencer region of the sequence before the promoter which initiates transcription.

The mRNA produced due to mutated DNA sequence after the deletion or insertion point will be read as out of frame thus resulting in nonsense protein.