Oogenesis and its process_Physic Chemistry Biology

 Oogenesis and its process

This topic is available on the class 12 Biology book chapter number 3 human reproduction 

                 5 mark 

Board examination question

Ans. The process of formation of a mature female gamete is called oogenesis 

The process of oogenesis are divided into three categories multiplication phase, growth phase and maturation phase 

a). Multiplication phase:-In this phase the germ cells of the germinal epithelium of the ovary repeatedly divided mitotically to produce a larger numbers of dipole oogonia or egg mother cells.When cell division stops they are called oocyte.

b). Growth phase:-in this phase the oocytes increase in size in several time due to accumulation of Yolk.The enlarged oocyte with yolk is known as primary oocyte.

c).Maturation face:-The growth phases followed by the maturation phase.During this phase the primary oocyte undergo two successive division called maturation division 

The first maturation division is reduction division producing two unequal haploid daughter cells.The smaller being the first polar body and the larger one is called secondary oocyte or Ootid.The secondary oocyte undergoes second maturation division in which a larger sized ovum and a small second polar body is formed. The first polar body also divides mitotically into two equal sized secondary polar bodies. The polar bodies do not play any role in reproduction and they degenerate.

Thus the primary oocyte, instead of forming four ova of equal size, gives rise to a single large ovum and three small polar bodies.the secondary oocyte or Ootid transforms into mature egg or ovum and get ready for fertilization.