Question

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

• A. It has far less cytoplasm, as well as less DNA than in an uncleaved zygote.
• B. It has more or less equal quantity of cytoplasm and DNA as in uncleaved zygote.
• C. It has more cytoplasm and more DNA than an uncleaved zygote.
• D. It has almost equal quantity of cytoplasm, as an uncleaved zygote but much more DNA.

Answer 1

The correct option is D It has almost equal quantity of cytoplasm, as an uncleaved zygote but much more DNA.

After fertilization, the zygote undergoes cleavage, first produces 2-celled embryo. Then each of these cells undergoes mitosis and divides, bringing the number of cells to 4. Repeated divisions increase the number of cells, called as blastomeres, that make up the embryo. At about the 32-cell stage the embryo is a solid ball of blastomeres called a morula. A morula will have almost same amount of cytoplasm as the zygote but a significantly increased amount of DNA due to rapid divisions of cleavage.

Therefore, the correct answer is option D.