Biology - Human Reproduction Question with Solution | TestHub
Identify the CORRECT statement about CLEAVAGE in HUMAN ZYGOTE.
Statement (I): Cleavage is holoblastic.
Statement (II): First cleavage is meridional.
Statement (III): Second cleavage is horizontal.
Statement (IV): Third cleavage is horizontal.
In light of the above statements, choose themost appropriateanswer from the options given below.
Options:
Answer:
Solution:
Cleavage in the human zygote is holoblastic because the egg is almost alecithal or microlecithal, meaning it contains very little yolk. Thus, Statement I is correct.
The first cleavage division is meridional, passing through the animal-vegetal axis to form two blastomeres. Thus, Statement II is correct.
Mammals exhibit rotational cleavage. During the second cleavage, one blastomere divides meridionally while the other divides equatorially. Therefore, stating the second cleavage is purely horizontal is incorrect. Thus, Statement III is incorrect.
Subsequent cleavages in mammals are highly asynchronous and do not follow a strict synchronized pattern of horizontal or equatorial planes as seen in amphibians. The typical generalized third horizontal cleavage does not apply to the human embryo. Thus, Statement IV is incorrect.
Therefore, only statements I and II are correct.
Answer: Only I and II are correct
