In which of the following transmission, meiosis occurs:

Ans. is 'a' i.e. Primary to secondary spermatocyte Meiosis is a special type of cell division that reduces the number of chromosomes to the haploid number of 23 (from diploid number 46). It takes place in germ cells only; to give rise to gametes (sperms and egg cells) It involves two meiotic cell divisions, meiosis I & meiosis II.The first mitotic division is a reduction division because the chromosome number is reduced from diploid (46) to haploid (23).The 2nd meiotic division is similar to mitosis as daughter cells formed contain the same haploid number of chromosomes as the mother cell.Steps of spermatogenesisSpermatogenesis which begins at puberty is the process which converts spermatogonia into mature sperms or spermatozoa.At or shortly before puberty, primordial germs cells in the seminiferous tubules, divide mitotically into spermatogoniaI stem cells. These stem cells give rise to type A spermatogoniaType A spermatogonia undergo mitotic divisions to form a clone of type A cells. The last cell division produces type B spermatogoniumSpermiogenesis is the process which transform spermatid into sperms or spermatozoa.