Condensed Gametogenesis Lecture PDF

HAPS Anatomy & Physiology LOs: Reproductive System Comparison of male and female gametogenesis – Compare and contrast the timing and number of oocytes produced in oogenesis and sperm produced in spermatogenesis. – Compare and contrast endocrine regulation of spermatogenesis a...

HAPS Anatomy & Physiology LOs: Reproductive System Comparison of male and female gametogenesis – Compare and contrast the timing and number of oocytes produced in oogenesis and sperm produced in spermatogenesis. – Compare and contrast endocrine regulation of spermatogenesis and oogenesis.  Mitosis and Meiosis Two fundamental cell types – Somatic Cells Cells that are the building blocks of the body Undergo mitosis Cell division gives rise to two genetically identical daughter cells in which the total number of chromosomes is maintained (diploid) – Germ Cells Produce gametes (sperm and egg cells) Undergo mitosis AND meiosis Two rounds of cell division ultimately give rise to cells that each contain one copy of each chromosome (haploid)  Cell division by Mitosis Cells double their chromosomes (replication) and this results in two identical copies of each chromosome (sister chromatids) Divide chromosomes evenly Split into two “daughter” cells that are identical to one another and have the same number of chromosomes as the original cell (diploid, 2n)  Cell Division by Meiosis Two stage process that involves two successive cell divisions: Meiosis I and Meiosis II Meiosis I – Replication (like mitosis) – Homologous chromosome pairs line up and separate – Reduces the chromosome number from diploid (2n) to haploid (1n) Meiosis II – No replication – Sister chromatids separate – Four haploid (1n) cells are produced, each containing one copy of each chromosome Meiosis Produces New Combinations of Genes in Two Ways Independent or random assortment – Metaphase I – Maternal and paternal homologues divide randomly – Results in a gametes having a unique combination of chromosomes Crossing over – Prophase I – The exchange of chromosome segments between homologous pair  Gametogenesis and Fertilization Gametogenesis – Spermatogenesis Production of sperm (male gamete) – Oogenesis Production of egg (female gamete) Fertilization – Fusion of the nuclei of male and female gametes – Each gamete contributes 50% of genetic material (DNA) needed to make an organism  Gametogenesis: Spermatogenesis 1. Spermatogonia Stem Cells (diploid) – Continually undergo mitosis – Some daughters will become primary spermatocytes – Some become spermatogonia 2. Primary Spermatocytes (diploid) – Begin Meiosis I (independent assortment and crossing over occur here) – Results in two secondary spermatocytes 3. Secondary Spermatocytes (haploid) – Undergo Meiosis II – Results in four spermatids 4. Spermatids (haploid) – Mature into sperm cells by the process of spermiogenesis  Spermiogenesis Differentiation of Spermiation – Release of sperm Spermatids heads from Sertoli – Acrosomal vesicle forms (Nurse) cells – Flagellum produced – Free to move – Mitochondria gather around through duct and participate in flagellum ejaculation and – Excess cytoplasm lost fertilization  Spermatozoa Anatomy Head – Nucleus and Acrosome Mid Piece – Mitochondria for energy Tail – Whip-like – Only flagellum in human body  Gametogenesis: Oogenesis 1. Oogonia Stem Cells (diploid) – Undergo mitosis before birth – Some daughters will become primary oocytes 2. Primary Oocyte (diploid) – Proceed towards Meiosis I but the process stops until female reaches puberty – Each month during the ovarian cycle, some primary oocytes are simulated to complete Meiosis I (independent assortment and crossing over occur) – Cytoplasm divides unevenly and haploid this results in one secondary oocyte (haploid) and one polar body 3. Secondary oocyte (haploid) – Proceeds towards Meiosis II but the process stops until fertilization occurs – If fertilization occurs, Meiosis II continues, and another polar body is Spermatogenisis vs. Oogenesis Similar…. But many differences Location – Testes vs Ovaries Meiotic Division of Cells – Equal vs unequal distribution of cytoplasm Number of Gametes Produced – 4 vs 1 ovum and 2 polar bodies Size of Gametes Produced – Small sperm vs large ovum Release of Gametes – Continuous vs monthly cycle Onset – Puberty vs prenatal Duration – Uninterrupted process vs interrupted End – Lifelong vs terminates with menopause Claire Johnson, Stanley Stupski, Dylan Bard,