Sex and genetics: Gametogenesis

Cell Biology Course Sex and genetics: Gametogenesis PhD Nguyen, Lai Thanh Dept of Cytoloty, Histology, Embyology and Biophysics Hà Nội -21/03/2013 Objectives  Benefits of sex?  Meiosis?  Gametogenesis? Asexual reproduction generate the offsprings genetically identical to parent Sexual reproduction rise the diversity Benefits of sex  The simple genetic resourse of asexual reproductive organisms  The diversity of genetic in sexual reproductive organisms  Different, atractive in males and females? The differents between males and females  In appearance  In behavior  The most important is the gametes they produce  They fascinate the other to lead the integration of two types of gametes Why gametes is important? Males produce sperms – the motile gametes Females produce eggs – the nonmotile gametes Sperm and egg can merge together in fertilization process to form zygote From one-cell structure of zygote, the individual will take shape with specific characteristics inherited from parents and his own features distinct from others What is the mystery? Meiosis leads to haploid gametes The process of meiosis involve in two steps: meiosis I and meiosis II All the particularities of meiosis occur in meiosis I, mainly in prophase I Meiosis produces haploid gametes Prophase I with special chromosome pairing Leptotene During this stage, individual chromosomes begin to condense into long strands within the nucleus http://www.corbisimages.com/images/Corbis-42-26624178.jpg?size=67&uid=ea0870c9-7872-4af4-911a-5a17982acb8f http://my.opera.com/kiyoshi/albums/showpic.dml?album=164047&picture=2428575 Prosess of meiosis Meiosis may go wrong Down Syndrome Function of sex chromosome Gametogenesis Oogenesis At month 7th of pregnant period, there are about million of oocytes and all are arrested at diplotene stage of meiosis I Oogenesis pauses in a half way when the the girl is born Oogenesis Oogenesis Spermatogenesis In the male spermatogenesis occurs from puberty to old age The spermatozoa produced from spermatogonium Spermatogenesis Not as oogenesis, the number of spermatogonium are maintained because they can self renew Spermiogenesis The following are the major events that occur during spermatogenesis: Formation of Acrosome (from the Golgi) at the front end of the sperm Formation of flagellum results due to elongation of microtubules (9+2 axoneme) from distal centriole at the base of the nucleus Nuclear Shaping & Condensation occurs due to changes in chromatin packaging (change from somatic histones to sperm-specific protamines) Rearrangement of organelles (e.g., mitochodria, centrioles); Mitochondria fuse and form spiral around anterior portion of axoneme of flagellum in the midpiece region Shedding of the Residual Body Most of the cytoplasm is lost; sperm becomes more streamlined Objectives Quá trình giảm phân Phân biệt loại tế bào trình giảm phân Đặc trưng của tế bào ở kỳ đầu giảm phân Biến đổi của tinh tử thành tinh trùng Khác biệt giữa giảm phân tạo trứng giảm phân tạo tinh trùng Thank You ! ...Objectives  Benefits of sex?  Meiosis?  Gametogenesis? Asexual reproduction generate the offsprings genetically identical to parent Sexual reproduction rise the diversity Benefits of sex  The simple... resourse of asexual reproductive organisms  The diversity of genetic in sexual reproductive organisms  Different, atractive in males and females? The differents between males and females ... to coil and so become shorter and thicker The nuclear envelope starts to degenerate The spindle formation is on process Nucleolus disappears Metaphase I: paires of chromosomes orient randomly