If an adult hamster with a 24-hour endogenous rhythm receives a lesion to the SCN and a subsequent SCN transplant from a young hamster with an endogenous rhythm of 20 hours, which outcome occurs?
A) The adult hamster will be arrhythmic.
B) The adult hamster will adopt a 20-hour rhythm.
C) The adult hamster will regain its original 24-hour rhythm.
D) The adult hamster will fail to entrain to the light-dark cycle.

Question

Quizplus · Accepted Answer

The SCN is the master pacemaker that generates the circadian rhythm in mammals. Lesioning the SCN would destroy the pacemaker and the circadian rhythm. However, if an SCN transplant is given, it will re-establish the pacemaker and rhythm. In this case, because the adult hamster received an SCN transplant from a young hamster with a 20-hour endogenous rhythm, the adult hamster will adopt the rhythm of the donor hamster, and thus will have a 20-hour rhythm instead of its original 24-hour rhythm.

If an Adult Hamster with a 24-Hour Endogenous Rhythm Receives