Gametogenesis Notes PDF

13/09/2024 Gametogenesis Gametogenesis: The production Conversion of of g...

13/09/2024 Gametogenesis Gametogenesis: The production Conversion of of gametes from Germ Cells into haploid precursor cells. Male and Female Gametes Prepared by: Judith Clarisse Tan 1 2 Clinical Correlates: Primordial Germ Cells Teratomas Gametes are derived from Primordial Tumors that contain variety of Germ Cells (PGCs) that are formed in tissues, such as bones, muscles, the epiblast during the 2nd week of embryonic development and move to hair, gut epithelia etc. the wall of the yolk sac. May have arise from pluripotent At 4th week, these PGCs migrate stem cells. towards the developing gonads, Evidences suggests that arriving at the end of the 5th week. teratomas arise from PGCs strayed from their original EPIBLAST migratory paths, or epiblast cells Gives rise to all 3 germ layers, and the primordial germ cells. forming the three germ layers during gastrulation. 3 4  13/09/2024 Chromosome Theory of Chromosome Theory of Inheritance Inheritance Traits of a new individual are determined by specific genes on chromosomes inherited from the father and the mother. Each chromosome Humans have approx. 23,000 genes on 46 chromosomes pair is homologous, Genes on the same chromosomes tend to be inherited together and so are one coming from the known as linked genes. female gamete, one from the male gamete. 22 of the human chromosomes are autosomes, while one pair is the sex chromosomes 5 6 Sex Determination Sex Determination Primary Sex Determination SRY Gene – Sex-determining region of the Y chromosome – Codes for the protein testis-determining factor (TDF) – Transforms bipotential gonad into a testis 7 8  13/09/2024 Sex Determination Bipotential to Specific Gonads 2 precursor organs: 1. Wolffian duct – differentiates into the structure of the male genital tract Müllerian inhibiting hormone - causes the Müllerian ducts to atrophy instead of developing into the oviducts and uterus 2. Müllerian duct – source of the female reproductive organs 9 10 Mitosis S Phase One somatic cell divides giving rise to two identical daughter cells. Each daughter cell receives the complete complement of 46 chromosomes. Before mitosis, each chromosome replicates its DNA. 11 12  13/09/2024 Meiosis Cell division that takes place in gametes to generate male and female gametes. Requires two divisions to reduce the number of chromosomes by half, producing haploid daughter cells. 13 14 DNA Replication DNA Replication Synapsis Synapsis Crossing-Over Crossing-Over – Chiasma – Chiasma In humans, at the end of In humans, at the end of meiosis I, each daughter cell meiosis I, each daughter cell will only have 23 unique will only have 23 unique chromosomes (haploid) chromosomes (haploid) 15 16  13/09/2024 DNA Replication Synapsis Crossing-Over – Chiasma In humans, at the end of meiosis I, each daughter cell will only have 23 unique chromosomes (haploid) 17 18 19