Question

During reproduction, the chromosome number ($2n$) reduces to half ($n$) in the gametes and again the original number ($2n$) is restored in the offspring. What are the processes through which these events take place?

Answer 1

Gametogenesis

Gametogenesis is the process of formation of the gametes. Oogonia and spermatogonia undergoes meiotic divisions to form the ovum and the sperms respectively.

Meiotic divisions are reductional in nature and lead to the reduction of the chromosome number in the daughter cells (haploid) when compared to the parent cell. Thus, the chromosome number is half ($n$) in gametes.

Fertilisation

Fertilisation involves the fusion of haploid gametes to form diploid zygote. This restores the chromosome number of the offspring back to diploid ($2n$).