Question

Write a brief note on three stages of gametogenesis.

Answer 1

Gametogenesis includes spermatogenesis & oogenesis. It includes three phases -

1. Multiplication Phase - In this phase, the diploid germ cell divides by mitosis to form diploid oogonia in oogenesis & spermatogonia in spermatogenesis.
2. Growth Phase - This phase involves only growth in size. It is the longest phase. It results in the formation of the primary oocyte in oogenesis and primary spermatocyte in spermatogenesis.
3. Maturation Phase - This phase involves meiotic division and it is divided into two phases -

• Maturation - I - The diploid primary oocyte/ spermatocyte divides by meiosis-I to form two haploid secondary spermatocytes in spermatogenesis and in oogenesis one secondary oocyte & one polar body is formed.
• Maturation - II - In spermatogenesis, the two secondary spermatocytes divide by meiosis-II to form four haploid spermatids which finally convert into four haploid sperms. In oogenesis, the secondary oocyte divides by meiosis-II to form one haploid ootid and one haploid polar body-II.