Reproduction I PDF - Fall 2023

Reproduction I November 20, 2023 1:19 PM Super Seven List – Reproduction (9 MCQs) 1. Oogenesis and spermatogenesis: what are they? review meiosis and clinical implications for heredity / inheritance 2. Characteristics of male and female reproductive system, sex hormones (effects on cells): main ch...

Reproduction I November 20, 2023 1:19 PM Super Seven List – Reproduction (9 MCQs) 1. Oogenesis and spermatogenesis: what are they? review meiosis and clinical implications for heredity / inheritance 2. Characteristics of male and female reproductive system, sex hormones (effects on cells): main characteristics, cellular mechanism of action 3. Menstrual cycle: from gonadotropins, to ovary to hormones to endometrium 4. Fertilization (oocyte to zygote to embryo to fetus) and fetal development (reviewing timelines) 5. Hormonal induction of labour, lactation, feedback mechanisms 6. Genes, chromosomes and heredity - Primary function to produce gametes - Normal: 22 pairs autosomes 1 pair of sex chromosomes Week 11 Page 1 - Normal: 22 pairs autosomes 1 pair of sex chromosomes Homologous - during cell division (mitosis/meiosis) Germ cells (oocytes and sperm cell)- each have 23 chromosomes, not 23 pairs Gametogenesis - production of sex cells Zygote - 23 of sperm and 23 oocytes together - Australia - background - Ability to make sex chromosome - Mitosis Most of what's done in body - start with cell, divides, and divides to exactly original Week 11 Page 2 ○ Most of what's done in body - start with cell, divides, and divides to exactly original - Meiosis - start with 4 chrom, divide, but not all 23 pairs dividing equally, and with gametes, can look radically diff from original - Mitosis: ○ 23 pairs of chromosomes ○ 1 from maternal and 1 from paternal ○ start with cell division - maternal and paternal replicate identically, and line up - Meiosis: ○ Maternal and paternal chromosomes undergo replication - forming a tetrad (a pair of replicated homologous chromosomes) ○ Tetrad randomly aligns at metaphase plate, and then chunks of information is exchanged, via cross over  Instead of lining underneath each other, align side-by-side/randomly for crossover of info ○ Homologous chromosomes separate, while sister chromatids stay together (end of anaphase I) ○ (meiosis II) Final stage is to separate the sister chromatids, so left with 4 daughter cells with 23 chromosomes (anaphase II)  Ideally start with 1 and get 4 Week 11 Page 3 - In meiosis prophase I, homologous chromosomes synapse - A sister chromatid from each homologous chromosome exchanges positions (information) at a particular segment, this cross over is called a chiasma - Chiasma breaks - At end of meiosis I, end up with 4 chromosomes (4 haploid gametes), and 2 of these 4 chromosomes are recombinant (carry new combinations of genes) - By the end, no longer have identical cells - Information for diff categories i.e. eye colour, but not same Week 11 Page 4 - Takes place in testes seminiferous tubules, starts to happen at puberty - Prior to puberty, start with spermatogonium that divides by mitosis ○ Some remain as precursor stem cells - At puberty, spermatogonium moves down to meiosis division ○ Meiosis I - primary spermatocyte replicates, forms tetrad, has crossing-over = secondary spermatocyte ○ Meiosis II - secondary spermatocyte separates into chromosomes into chromatids = spermatid  Spermiogenesis - spermatids separate into 4 spermatozoa in lumen of seminiferous tubules Week 11 Page 5 - Spermiogenesis occurs within 24 days - Making sperm cell, getting rid of excess cytoplasm, making it motile, condensing head--with 23 chromosomes - Entire process is 24 days, but can make 200-300 sperm per day Week 11 Page 6 - Start with oogonium, this happens in fetal development - Mitosis of oogonium into primary oocyte occurs in early fetal life - Meiosis I of primary oocyte begins in fetal development - At puberty, primary oocyte completes meiosis I-->producing secondary oocyte + first polar body ○ Secondary oocyte begins meiosis II, which is then ovulated - At fertilization, meiosis II resumes and splits into ovum and second polar body - Once nuclei of sperm cell and ovum unit, this forms a diploid zygote - Don't make new primary or secondary oocytes in puberty - All eggs are made in fetus for life - Meiosis ○ Happens in puberty Oocyte released in ovulation Week 11 Page 7 ○ Oocyte released in ovulation ○ Final division occurs when fertilized with sperm - Mitosis = germ cell proliferation: 46 chromosomes undergo cell division(23 pairs, 2n) = germ cell/oogonium/spermatogonium ○ Females: occurs in fetus ○ Males: occurs until puberty - Meiosis begins: the DNA replicates (no cell division), so still have 46 chromosomes, but now 46 pairs (4n) = primary oocyte/spermatocyte ○ Female: fetal stage ○ Males: begins at puberty - Meiosis I completed: primary gamete divides into 1 secondary oocyte(+ first polar body)/ 2 spermatocytes (23 chromosomes, 2n) ○ Female: begins at puberty ○ Male: continues from puberty - Meiosis II: secondary gamete divides to produce 1 egg/4 sperm (23 haploid chromosomes, 1n) Week 11 Page 8 - Meiosis II: secondary gamete divides to produce 1 egg/4 sperm (23 haploid chromosomes, 1n) - For males, meiosis starts at puberty--1 primary spermatocyte produces 4 sperm, which happens throughout lifetime - For females, 1 primary oocyte produces 1 egg/primordial follicles ○ start with 7 million eggs at birth, but many undergo atresia, and avg lifetime females ovulation 400-500 - Final phase of meiosis is fertilization Produce games: - Females stop at age of 50 at menopause, no further release of eggs - Males generate sperm cells throughout life Week 11 Page 9