Question

Explain the process of oogenesis in humans.

Answer 1

The phenomenon of formation of haploid ova(egg) from the diploid egg mother cells of the ovary(female gonad) is called oogenesis. It occurs in three phases i.e., Multiplication phase, growth phase and maturation phase. In the multiplication phase, some cells of the germinal epithelium of ovary function as primary germ cells and are called oogonia, which multiply by repeated mitotic division and become primary oocytes when cell division ceases. In the growth phase, the increase in the size of the primary oocyte is very considerable. It is a slow process and may take a long period. In human female, the oogonia are already formed at the time of birth and continue growth only after attaining sexual maturity. It contains a diploid number of chromosomes. In the maturation phase, the primary oocyte undergoes first meiotic division and gives rise to two daughter cells, larger one called secondary oocyte and a smaller one as a first polar body. The secondary oocyte divides again and gives rise to haploid ootid or the ovum and the second polar body. Thus, one ovum is formed from one primary oocyte as a result of oogenesis.