Embryology question

[Ritsmitu]

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Hey

I am having troubles with embryo questions...I read Barrons DAT and Kaplans DAT books and still not getting these questions.

so there is this one question from the sample DAT

It says:
Of the following, the rate and type of cleavage occurring after fertilization would be most affected by the:

A. Amount and distribution of yolk.
B. number of chromosomes
C. thickness of the cell membrane
D. Temperature
E. Thickness of the zona pellucida
The answer is A. 😕

Also what is zona pellucida?

thanks

 

[jntm46]

If you wiki cleavage, it'll tell you "Depending mostly on the amount of yolk in the egg, the cleavage can be holoblastic (total or entire cleavage) or meroblastic (partial cleavage). The pole of the egg with the highest concentration of yolk is referred to as the vegetal pole while the opposite is referred to as the animal pole."

The zona pellucida is a gylcoprotein layer surrounding the plasma membrane of an oocyte, it insures that that fertilization occurs only between egg and sperm of the same species.

You can always google or wiki something you don't understand. Mostly likely, you'll find the answers on wiki.

Hope this helps.

 

[FutureDental88]

Cleavage is related to Yolk. It occurs only in the non-yolky cytoplasm .

It has nothing to do with the other alternatives.