Final answer:
The experimental manipulation that would most likely hasten mRNA degradation in a eukaryotic cell is increased polyadenylation of mRNA (option A).
Step-by-step explanation:
The experimental manipulation that would most likely hasten mRNA degradation in a eukaryotic cell is increased polyadenylation of mRNA (option A).
Polyadenylation is a post-transcriptional modification in which a chain of adenine nucleotides is added to the 3' end of the mRNA.
This modification, known as the poly-A tail, plays a role in mRNA stability.
Increasing polyadenylation would lead to shorter poly-A tails, resulting in faster mRNA degradation.
The poly-A tail helps protect the mRNA from exonuclease activity, which is an enzyme that degrades unprotected RNAs.
Therefore, inhibition of exonuclease activity (option B) would actually slow down mRNA degradation rather than hasten it.