Looking for classes? Ksquare Career Institute, Bengaluru →
Which one of the following statements about morula in humans is correct?
A
It has more cytoplasm and more DNA than an uncleaved zygote
B
It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA
C
It has far less cytoplasm as well as less DNA than in an uncleaved zygote
D
It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygote
Detailed Solution
The morula is the solid ball of 8–16 blastomeres formed by cleavage of the zygote.
Cleavage divisions are rapid mitotic divisions without any growth phase in between; the zygote is simply partitioned into smaller and smaller cells, so the total amount of cytoplasm stays almost the same as in the zygote.
Before each division, however, the DNA is replicated, so every blastomere has a full diploid set.
A morula with 16 cells therefore contains about 16 times the DNA of the uncleaved zygote.
Hence the morula has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA.
Cleavage divisions are rapid mitotic divisions without any growth phase in between; the zygote is simply partitioned into smaller and smaller cells, so the total amount of cytoplasm stays almost the same as in the zygote.
Before each division, however, the DNA is replicated, so every blastomere has a full diploid set.
A morula with 16 cells therefore contains about 16 times the DNA of the uncleaved zygote.
Hence the morula has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA.