ANAT 2130 Lecture Notes - Lecture 2: Down Syndrome, Gametogenesis, Gamete
16 Oct 2016
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Document Summary
Special population of somatic cells set aside early in development to become gametogenic cells lines in ovary (oogonia) and testis (spermatogonia) Oogonia and spermatogenic also mitotically active but then enter meiosis. Diploid cell line one gonads produces haploid gametes. Meiosis reduces diploid chromosome number to haploid chromosome number. When haploid gametes recombine, diploidy reestablished in zygote. Diploid oogonia or spermatogonia are mitotic cells. Diploid primary cyte has chromosome duplication > tetraploid cell (4n dna) Meiosis i > secondary cyte > diploid cell (2n dna) Meiosis ii > haploid gamete (1n dna) One pgc becomes many gonia which in turn become many 1degree cytes: in primary cytes, homologous chromosomes pair and then dna duplicates. One 1degree cyte divides to produce two 2degree cytes: homologs separate without centromere division. Two 2degree cytes divide to produce two haploid gametes: centromeres divide to separate duplicated dna strands. Thus, one 1degree cyte yields four gametes.
