Zoology - Human Reproduction Question with Solution | TestHub

At about 30 to 36 hours of fertilisation, the zygote moves through the isthmus of oviduct to uterus and divides mitotically by a process called cleavage which results into two smaller cells called blastomeres. A second cleavage occurs which results in the formation of 4 cells. Cleavage continues to occur and results in a solid ball of cells i.e. morula having 16 cells (occasionally 32). Since the divisions are mitotic, therefore the size of morula is same as that of zygote because with each cleavage division, number of cells increases but their size decreases. Due to mitotic divisions, content of cytoplasm of morula is same as that of zygote but DNA content is increased as each cell has its own DNA. So, the correct answer is 'It has almost equal quantity of cytoplasm as an uncleaved zygote but much more DNA'.