Reproductive Physiology Primordial Germ Cells - from Yolk Sac these migrate to fetus when it is 5 weeks old - these cells give rise to the gonads (ovaries for female, testes for male) first they form the gonadal ridge There are 46 chromosomes in most of our cells, 23 from Mom, 23 from Dad so these 46 chromosomes exist as 23 PAIRS numbering 1 23. The two chromosomes of the 23rd pair are know as the Sex Chromosomes. Females have two X chromosomes, XX one from Mom (maternal), one from Dad (paternal) Males have one X chromosome from Mom and one Y chromosome from Dad Mom s oocytes (eggs) can only carry an X chromosome Dad s sperm may carry either an X or a Y so if an X carrying sperm fertilizes the egg there will be a female baby..if a Y carrying sperm fertilizes the egg there will be a male baby. There are many genes on the X chromosome, but very few on the Y (mostly maleness ) If there is a gene on the X such as Red or Green color perception, no such gene is on the Y chromosome so if the X-Red/Green gene is mutated, the male baby will be color blind. These are Sex-Linked Traits.
Some Sex-Linked Traits Agammaglobulinemia Albinism - various forms Albright's osteodystrophy Aldrich Syndrome - immunological disorder Anemia, Angiokeratoma Muscular dystrophy, Duchenne type Cerebellar Ataxia Cerebral Sclerosis, Scholz Type Charcot-Marie-Tooth = peroneal atrophy Choroideremia - progressive blindness Cleft Palate Color Blindness - Red & Green Deafness Diabetes Insipidus -several types Dyskeratosis Ectodermal Dysplasia Ehlers-Danlos syndrome Endocardial Fibroelastosis Faciogenital dysplasia
More Sex-Linked Traits Fibrin-stabilizing factor deficiency Focal dermal hypoplasia Glucose-6-Phosphate dehydrogenase deficiency Glycogen storage disease Granulomatous disease Hemophilia A Hemophilia B (Christmas disease) Hydrocephalus Hypochromic Becker type (onset >< age 30-40) Hypomagnesemic tetany Hypophosphatemia (vitamin D resistant rickets) Hypoplasia of Addison's diseade Hypoxanthine guanine phosph-oribosyl transferase deficiency Ichthyosis (epidermal scaling) Incontinentia pigmentii Iris Lowe's oculocerebrorenal syndrome Megalocornea Menkes Syndrome (kinky hair disease) Mental deficiency
And Even More Sex-Linked Traits Microphthalmia Mucopolysaccharidosis II Muscular dystrophy, progressive Muscular dystrophy, tardive, Night blindness Norrie's disease (blindness) Nystagmus (one type) Ophthalmoplegia (myopia) Oral-facial-digital syndrome Parkinsonism (one type) Pelizaeus-Merzbacher disease Phosphoglycerate kinase deficiency Pituitary dwarfism Pseudohermaphroditism, male Reticuloendotheliosis (bruising tendency) Retinitis pigmentosa (blindness) Retinoschisis Spastic paraplegia Spinal and bulbar muscular atrophy Spinal ataxia Spondylo-epiphyseal dysplasia, late
Next to the Gonadal Ridge there are two series of structures, one with the potential to develop into a Male, and one with the potential to develop into a female - so at first all human embryos have both of these 1. Mesonephric (Wolffian) Duct for male 2. Paramesonephric (Müllerian) Duct for female - both are present in all early fetuses
Male Development - Y Chromosome has the SRY gene - Sex-Determining Region of Y (SRY) the gene that codes for the protein known as Testis-Determining Factor (TDF) which regulates the development of the testes - Testes produce the following: 1. Testosterone male hormone for development of primary & secondary male characteristics - male genitalia - hair distribution, fat distribution, thicker/courser hair, > melanin, sebaceous secretions, hypertrophy of larynx, > metabolism, > RBC s, > protein synthesis (mass) 2. Anti-Müllerian Hormone (AMH) - causes the regression of the female-forming Paramesonephric Ducts (Mullerian Ducts) which allows the development of the Male-forming Mesonephric Ducts (Wolffian Ducts)...that's right, MALE fetuses have to suppress the development of the FEMALE reproductive tract, otherwise they would develop as females - they would have testes, but they would not descend (drop). They may appear in every aspect as "female"...so, are we all FEMALE by default :) Unless the SRY and AMH work? Check out Androgen-Insensitivity Syndrome or Testicular Feminization on page 1021 - Müllerian (Paramesonephric) Ducts regress and remain as Appendix of Epididymis and Appendix of Testis
Somatic Cells (Greek for body ) a type of cell forming most of the organisms body i.e. any cell other than the gametes (oocytes or sperm) - Nuclear division is via MITOSIS Germ Cells a specialized cell giving rise to the gametes (oocytes/eggs or sperm) - Nuclear division is via MEIOSIS - Meiosis - this type of nuclear division is different from Mitosis. Mitosis is regular ole' cell division (actually nuclear division) where a Diploid cell divides to give rise to two Diploid daughter cells. In other words, a cell w/ 46 chromosomes, duplicates each to make 2 daughter cells w/ 46 chromosomes each...that's mitosis - Meiosis - this is Gametogenesis or the production of the gamest, egg and sperm so you begin with a Diploid cell with 46 chromosomes but you end up with 4 Haploid cells, each with only 23 chromosomes - Diploid - the cell has two sets of 23 chromosomes for a total of 46 chromosomes...1 set of 23 from Momma and 1 set of 23 from Daddy - Haploid - in the making of sperm and eggs via meiosis, the chromosomal number is cut in half to 23 chromosomes per cell - notice that gametes have half the normal number of chromosomes 1. Spermatogenesis - production of sperm 2. Oogenesis - production of oocytes (eggs)