Introduction to Human Inheritance

P1: Explain how sperm and ova are formed by producing an annotated diagram of meiosis and discussing what happens in ogenesis and spermatogenesis In the male, meiosis precedes sex cell differentiation. A single spermatogonium enters the first meiotic division as a primary spermatocyte. This division produces two secondary spermatocytes, each of which divides to form two haploid spermatids. Each spermatid then differentiates (by a process called spermiogenesis) into a spermatozoon by the elaboration of structural and functional specialisations that enable the sperm to fertilize the egg. Consequently, four haploid sperm result from each diploid spermatogonium. Sperm produced in the testicles are immature and not very motile. As the sperm make their journey through the tightly coiled epididymis, they mature and become motile. In relation to the diagram of spermatogenesis, each human Spermatogonium (germ stem cell) gives rise to many Spermatogonia by mitosis. So the number of chromosomes in each Spermatogonium cell is conserved at 46 chromosomes. Each Spermatogonium will then grow and develop into a Spermatocyte I which will duplicate its DNA so that each of its 46 chromosomes will have two chromatids per each chromosome at the end of the growth stage. Each Spermatocyte I will divide by Meiosis I (reductional meiosis) to give rise to two haploid. http://www.scienceaid.co.uk/biology/genetics/reproduction.html

Spermatocyte II each having 23 chromosomes and each chromosome is made up of two chromatids. Each Spermatocyte II will then divide by Meiosis II (equational meiosis) to give rise to two Spermatids. Each spermatid will have 23 chromosomes but the number of chromatids per chromosome is ONE.
Since the Spermatid only changes in shape and does not divide to produce a Sperm, the number of chromosomes and chromatids will stay the same as in the spermatid. The sperm will have 23 chromosomes (one chromatid per each chromosome).

Just like spermatogenesis,