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May 15 8:50 a.m. Make Up Exam For only one missed midterm Bring scantron and I.D. Sex Determination in Humans http://images.google.com/imgres?imgurl=www.goldenlands.com/Fox%2520network/simpsons/opcs/fullsize/Homer_Marge_opcC1394.jpg&imgrefurl=ht tp://www.goldenlands.com/Fox%2520network/simpsons/simpsonopc.html&h=700&w=694&prev=/images%3Fq%3Dhomer%2Band%2Bmarge%2Bsim pson%26start%3D20%26svnum%3D10%26hl%3Den%26lr%3D%26ie%3DUTF-8%26safe%3Doff%26sa%3DN Sex Determination in Humans – 5 stages Chromosomal Determination Gonad Differentiation Anatomical Differentiation Brain Differentiation Socialization Chromosomal Sex Determination EXAM Humans: 23 pairs of Chromosomes 22 pairs of Autosomes or Somatic Chromosomes (same in both sexes) 1 pair of Sex Chromosomes Males: 1 Y, 1 X = XY Females: 2 X = XX Human Male Karyotype, XY Chromosomes 1-22 are autosomes or somatic chromosomes; non-sex chromosomes XY are the sex chromosomes http://www.amnh.org/learn/musings/FA01/ia/HW_01.jpg Normal Human Female Karyotype; XX 22 pairs of autosomes 1 pair of sex chromosomes, XX X Y Y chromosome has less than 100 genes ……………….. One gene is for …… Additional genes found on Y chromosome Inability to see and hear the obvious gene Inability to express affection over the phone gene X Y Posturing in presence of other males gene Refusal to ask questions when lost gene Channel flipping gene Male Sports Bonding gene Addiction to death and destruction movies gene Preadolescent rock throwing gene Preadolescent attraction to spiders and insects gene Spitting gene EXAM Y chromosome Male anatomy, physiology, behavior SRY (HY) gene SRY (H-Y) protein X chromosome w/o SRY (HY) gene Female anatomy, physiology, behavior Primitive gonad or ovotestes = unspecialized H-Y Gene Testes Testosterone w/o H-Y Gene ovary Estrogens 2. Gonad Differentiation - Male H-Y or SRY Gene (on Y Chromosome) H-Y Protein (SRY protein) Inner part of ovotestes becomes testes Testes makes male hormones Male sex organs, secondary sex characteristics (muscle, skeleton), Brain development (for constant production of sperm) at 6 weeks 2.Gonad Differentiation – Female XX Absence of Y chromosome (no H-Y gene) Outer ovotestes develops into ovary at about week 12 Ovary produces female hormones: ~ sex organs ~ secondary sexual characteristics (muscle, skeleton) ~ absence of male hormones at week 6 allows brain to develop menstrual cycle at puberty. Little estrogen Mostly testosterone Little testosterone Mostly Estrogens Male Female Some abnormalities associated with X and Y chromosomes Crossing over of H-Y gene X Y X Spermatogenesis H-Y gene H-Y gene crosses over to X chromosome Y Sperm with X with H-Y gene X X X X Zygote: XX (genetic female) Egg with normal X without H-Y gene Phenotype = male, because of the H-Y gene Sperm with Y without H-Y gene Y Y X X Zygote: XY = genetic male Egg with normal X without H-Y gene Phenotype = female because of absence of H-Y gene Conclusion: EXAM Absence of H-Y gene usually = female; female is automatic unless H-Y gene is present Another Chromosomal Abnormality – Androgen Insensitivity XY Embryo Faulty Processing of testosterone Embryo not conditioned as male Embryo automatically develops into normal looking female Develops into female with XY chromosomes Normal breast development no uterus no oviducts vagina present internal testes present no sperm Primary Oocyte Non-disjunction Secondary Oocyte ovum zygote zygote Extra black chromosome sperm Missing a black chromosome Klinefelter’s Syndrome Klinefelter’s Syndrome – XXY+ 22 pairs of autosomes male with some female characteristics XX Egg + 22 autosomes XXY Zygote + 44 autosomes EXAM Y Sperm + 22 autosomes 1. Normal male until puberty, 2. Testes not normal, 3. Tall, 4. Female musculature, 5. Some breast development, 6. High pitched voice, 7. Usually sterile, 8. XXXY more extreme Trisomy X Syndrome – XXX+ 22 pairs of autosomes female XX Egg + 22 autosomes XXY Zygote + 44 autosomes EXAM X Sperm + 22 autosomes 1. 2, 3. 4. 5. 6. Normal Female, Normal appearance, May be sterile or fertile, May have mental retardation, 1 in 1200 births, XXXX more extreme Turner’s Syndrome = 22 pairs of autosomes and X0 Turner’s Syndrome – X0 + 22 pairs of autosomes female No X Egg + 22 autosomes EXAM X Sperm + 22 autosomes Characteristics: 1. Normal female until puberty, 2. Lack of normal ovary development, X0 Zygote + 44 autosomes 3. sterile 4. Remain childlike throughout life 5. Normal intelligence 6. 1 per 2500 births XYY Syndrome – XYY + 22 pairs of autosomes Male X Egg + 22 autosomes EXAM YY Sperm + 22 autosomes Male XYY Zygote + 44 autosomes Lower than normal intelligence Tall Aggressive – disproven Prison - disproven Early Death Syndrome – Y0 + 22 pairs of autosomes Male ? No X Egg + 22 autosomes Y0 Zygote + 44 autosomes EXAM Y Sperm + 22 autosomes Dies as embryo Too many genes missing with X All chromosomes are capable of forming a trisomy condition. The most common is chromosome 21. Trisomy 21 is also known as Down’s Syndrome Trisomy 21 – Down’s Syndrome 3 chromosome #21 Results in physical defects and mental retardation Frequency increases with mother’s age Why? Prophase I occurs before birth, Anaphase I occurs 12-50 years later in More ionizing radiation picked up in older woman’s lifetime resulting nondisjuctions Non-disjunction 21 21 21 21 Primary Oocyte Secondary Oocyte 21 21 21 21 21 ovum 21 21 21 zygote zygote Extra black chromosome 21 sperm Missing a black chromosome In Trisomy 21, chromosomes 21 do not separate after crossover Younger women 21 21 Older women EXAM Trisomy 21 increases with Mother’s age Triploid (3N) male karyotype – individual appeared normal except for slightly smaller lower jaw. This person also has Klinefelter, XXY Triploid Watermelon seedless Triploid carp - sterile Barr Body inactivates one of the X chromosomes in XX cells after embryo is properly developed sexually http://www.mun.ca/biology/scarr/Barr_Bodies.jpg XGreen XPink XX zygote Mitosis XG XG XP XP Mitosis Active XP Mitosis Active XG cell line cell line Female mosaic XGreen XGreen XX zygote Mitosis XG XG XG XG Mitosis Active XG Mitosis Active XG cell line cell line Female all green Anhidrotic Ectodermal Dysplasia: N = dominant, normal allele on X chromosome n = recessive allele carried on X chromosome resulting in no teeth and no sweat glands XNXN normal female XnXn female with few or no teeth and no sweat glands XNXn female parts of jaw with teeth and parts without teeth parts of skin with sweat glands, parts without sweat glands. XNY normal male XnY male with no teeth and no sweat glands No teeth, no sweat glands XNXn female http://www.bitein.com/images/reshma02.jpg Calico Cats (normally all females) B = allele for black fur, on X chromosome O = allele for orange fur, on X chromosome XBXB All black fur, female cat XOXO All orange fur, female cat XBXO Black and orange, female cat (Calico) XBY Black, male cat XOY Orange, male cat XBXOY XBXO Black and orange, male (Klinefelter, Calico) EXAM Conclusion – always one fewer Barr Body than X chromosomes Notice that two of the X chromosomes have Barr bodies causing them to be inactive