Describe the effect on the timing of midblastula transition

Describe the effect on the timing of mid-blastula transition of fertilizing the egg with three instead of only 1 sperm. What does this tell us about the mechanism by which the timing of the MBT is set?

Solution

Mid blastula transition (MBT) of the fertilised eggs are dependant on the nuclear : cytoplasmic ratio of the fused cell

if you add more sperm the indication is we add more DNA, the cytosolic volume of sperm is minimal

thus with 3 sperms the MBT timings will be reduced

this clearly indicates the MBT timing is set by the nucleus:cytoplasmic ratio

However, in some other organisms like Drosophilla MBT is cell cycle dependant