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The Living Body 4 - Sexual Reproduction.docx
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Department
Natural Science
Course
NATS 1610
Professor
Barbara Czaban
Semester
Winter

Description
NATS 1610 WINTER TERM L23 FORMING THE LIVING BODY Gametogenesis • Formation of gametes (via meiosis) − Spermatogenesis – sperm cells − Oogenesis – egg cells (oocytes) • Fertilization = union of egg + sperm produces fertilized egg (zygote) with DNA from both parents • Zygote cleaves to produce multicelled embryo − Each cell inherits the zygote’s DNA • Resulting offspring has traits inherited from both parents − As inherited from sperm and egg Spermatogenesis • GROWTH − Spermatogonium (diploid) male reproductive cell • MEIOSIS I, CYTOPLASMIC DIVISION − Primary spermatocyte (diploid) • MEIOSIS II, CYTOPLASMIC DIVISION − Secondary spermatocytes (haploid) − Spermatids (haploid) • CELL DIFFERENTIATION, SPERM FORMATION − Mature haploid male gametes Stages • Mitotic proliferation − Chromosomes in each cell: 46 (diploid number; single strands) − One daughter cell remains at the outer edge of the seminiferous tubule to maintain the germ cell line − One daughter cell moves toward the lumen to produce spermatozoa • Meiosis − Chromosomes in each cell: 46 (diploid number; double strands) − Primary spermatocytes – First meiotic division − Chromosomes in each cell: 23 (haploid number; double strands) − Secondary spermatocytes – Second meiotic division • Packaging − Chromosomes in each cell: 23 (haploid number; single strands) − Spermatids − Chromosomes in each cell: 23 (haploid number; single strands) − spermatozoa Oogenesis • GROWTH − Oogonia (diploid) female reproductive cell • MEIOSIS I, CYTOPLASMIC DIVISION − Primary oocyte (diploid) • MEIOSIS II
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