What effect does the deletion of the hst3 gene have on the lifespan of yeast in relation to the rtt gene?

• A. A. It compensates for the ∆rtt-induced decrease in lifespan.
• B. B. It has no effect on the ∆rtt-induced increase in lifespan.
• C. C. It compensates for the ∆hst3-induced decrease in lifespan.
• D. D. It has no effect on the ∆hst3-induced decrease in lifespan.

Answer: (B)

The correct answer indicates that the deletion of the hst3 gene does not influence the increase in lifespan caused by the deletion of the rtt gene. This outcome suggests that the mechanisms regulating lifespan and the effects of gene deletions are independent in this particular context.

When considering the relationship between rtt and hst3, it is important to understand the functions of these genes. The rtt gene is known to be involved in processes that promote longevity, while hst3 is related to histone deacetylation, which typically plays roles in cellular aging and stress responses. The deletion of the rtt gene may confer some longevity and, therefore, the presence or absence of hst3 would not further modify this increased lifespan.

This independence implies that the pathways influenced by rtt deletion are not significantly altered by changes in the expression or deletion of hst3, resulting in no effect on the lifespan that is increased due to the rtt deletion. Hence, the observation that the absence of hst3 does not alter the previously enhanced lifespan due to the deletion of rtt supports the conclusion of the correct choice.