Question

2n=16 in a primary spermatocyte whisch is in metaphase of first meiotic division. What shall be the total number of chromatids in each of the secondary spermatocyte?

Answer 1

During spermatogenesis, the secondary spermatocytes are produced when the diploid primary spermatocytes undergo meiosis I (reduction division). The single primary spermatocyte on completion of meiosis I produces two haploid secondary spermatocytes. Thus, the chromosome number in each spermatocyte will be half, here 8 chromosomes. Here only homologous chromosomes separate while the newly synthesised copy of DNA is still attached at centromere with the parental one.

Thus, the chromatids present in each secondary spermatocyte will be 16 because the newly synthesised copy of DNA replicated during S phase of meiosis I is still attached at the centromere to parental one.