Which one of the following statements about morula in human is correct?

Q. Which one of the following statements about morula in human is correct?

1. It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA
2. It has far less cytoplasm as well as less DNA than in an uncleaved zygote
3. It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygote
4. It has more cytoplasm and more DNA than an uncleaved zygote

Answer: It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA.

Morula in Human

·   A morula is an early-stage embryo consisting of 16 cells (called blastomeres) in a solid ball contained within the zona pellucida.

·   Cleavage differs from other forms of cell division in that it increases the number of cells and nuclear mass without increasing the cytoplasmic mass. This means that with each successive subdivision, there is roughly half the cytoplasm in each daughter cell than before that division, and thus the ratio of nuclear to cytoplasmic material increases.

·   Cleavage divisions are mitotic division, in which the single-celled zygote is converted into a multicellular morula. But during cleavage divisions, there is no growth of resultant daughter cells/blastomeres.

·   So, the DNA content will increase, but there is no increase or insignificant increase in the amount of protoplasm.

In embryology, cleavage is the division of cells in the early embryo. The process follows fertilization, with the transfer being triggered by the activation of a cyclin-dependent kinasecomplex. The zygotes of many species undergo rapid cell cycles with no significant overall growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called blastomeres and form a compact mass called the morula. Cleavage ends with the formation of the blastula.

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.