Which one of the following statements about morula in humans is correct? [2010]a)It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNAb)It has far less cytoplasm as well as less DNA than in an uncleaved zygotec)It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygoted)It has more cytoplasm and more DNA than an uncleaved zygoteCorrect answer is option 'A'. Can you explain this answer?

Question

Which one of the following statements about morula in humans is correct?  [2010]a)It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNAb)It has far less cytoplasm as well as less DNA than in an uncleaved zygotec)It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygoted)It has more cytoplasm and more DNA than an uncleaved zygoteCorrect answer is option 'A'. Can you explain this answer?

Answer

The rapid cell divisions that transform single-celled zygote into a multicellular structure is referred to as cleavage. The daughter cells produced by cleavage in zygote are termed as blastomeres. The first cleavage in zygote produces two cells which then divide to form four cells and so on. The 16-celled embryonic stage is referred to as a morula. The rapid cell divisions during cleavage in zygote are not accompanied by increase in cell mass. This is due to short interphase which results in a decrease in the size of blastomeres with increasing number as total cytoplasmic mass remains similar to that of a zygote. Thus, morula has almost same cytoplasmic mass as that of the zygote.

Since each cleavage division is accompanied by DNA replication and equal distribution of doubled DNA to daughter cells. Therefore, each cell division doubles the DNA content of morula,

Therefore, the correct answer is option A.

Answer

Morula is a solid ball contained within the zone pellucida. It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA.

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