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58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
58 ch13beyondmendel2008
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58 ch13beyondmendel2008

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  • The genes that we have covered so far affect only one phenotypic character, but most genes are pleiotropic
  • Duchenne muscular dystrophy affects one in 3,500 males born in the United States. Affected individuals rarely live past their early 20s. This disorder is due to the absence of an X-linked gene for a key muscle protein, called dystrophin. The disease is characterized by a progressive weakening of the muscles and loss of coordination.
  • Hemophilia is a sex-linked recessive trait defined by the absence of one or more clotting factors. These proteins normally slow and then stop bleeding. Individuals with hemophilia have prolonged bleeding because a firm clot forms slowly. Bleeding in muscles and joints can be painful and lead to serious damage. Individuals can be treated with intravenous injections of the missing protein.
  • The relative importance of genes & the environment in influencing human characteristics is a very old & hotly contested debate a single tree has leaves that vary in size, shape & color, depending on exposure to wind & sun for humans, nutrition influences height, exercise alters build, sun-tanning darkens the skin, and experience improves performance on intelligence tests even identical twins — genetic equals — accumulate phenotypic differences as a result of their unique experiences
  • Transcript

    • 1. Beyond Mendel’s Laws of InheritanceAP Biology 2006-2007
    • 2. Extending Mendelian genetics  Mendel worked with a simple system  peas are genetically simple  most traits are controlled by a single gene  each gene has only 2 alleles, 1 of which is completely dominant to the other  The relationship between genotype & phenotype is rarely that simpleAP Biology
    • 3. Incomplete dominance  Heterozygote shows an intermediate, blended phenotype  example:  RR = red flowers →RR  rr = white flowers →WW  Rr = pink flowers →RW  make 50% less colorAP Biology RR RW WW
    • 4. Incomplete dominance true-breeding X true-breeding P red flowers white flowers 100% pink flowers F1 generation 100% (hybrids) It’s like self-pollinate flipping 2 pennies! 25% 50% 25% red pink white 1:2:1 F2 generationAP Biology
    • 5. Co-dominance  2 alleles affect the phenotype equally & separately  not blended phenotype  human ABO blood groups  3 alleles  IA, IB, i  IA & IB alleles are co-dominant  glycoprotein antigens on RBC  IAIB = both antigens are produced  i allele recessive to bothAP Biology
    • 6. Genetics of Blood typepheno- antigen antibodies donation genotype type on RBC in blood status type A antigens A I I A A or A I i on surface of RBC anti-B antibodies __ type B antigens B IB IB or IB i on surface of RBC anti-A antibodies __ both type A & type B antigens universal AB IA IB on surface no antibodies recipient of RBC no antigens universal anti-A & anti-B O ii on surface of RBC antibodies donorAP Biology
    • 7. Pleiotropy  Most genes are pleiotropic  one gene affects more than one phenotypic character  1 gene affects more than 1 trait  dwarfism (achondroplasia)  gigantism (acromegaly)AP Biology
    • 8. Acromegaly: André the GiantAP Biology
    • 9. Inheritance pattern of Achondroplasia Aa x aa Aa x Aa dominant inheritance a a A a A Aa Aa A AA Aa dwarf dwarf lethal a aa aa a Aa aa 50% dwarf:50%AP Biology normal or 1:1 67% dwarf:33% normal or 2:1
    • 10. Epistasis  One gene completely masks another gene  coat color in mice = 2 separate genes  C,c: pigment (C) orB_C_ no pigment (c)  B,b:bbC_ more pigment (black=B) or less (brown=b)_ _cc  cc = albino, no matter B allele  9:3:3:1 becomes 9:3:4 How would you know that difference wasn’t random chance?AP Biology Chi-square test!
    • 11. Epistasis in Labrador retrievers  2 genes: (E,e) & (B,b)  pigment (E) or no pigment (e)  pigment concentration: black (B) to brown (b) eebb eeB– E–bb E–B–AP Biology
    • 12. Polygenic inheritance  Some phenotypes determined by additive effects of 2 or more genes on a single character  phenotypes on a continuum  human traits  skin color  height  weight  intelligence  behaviorsAP Biology
    • 13. Johnny & Edgar Winter Skin color: Albinism  However albinism can be inherited as a single gene trait  aa = albino albino Africansmelanin = universal brown color enzymetyrosine AP Biology melanin albinism
    • 14. OCA1 albino Bianca KnowltonAP Biology
    • 15. 1910 | 1933 Sex linked traits  Genes are on sex chromosomes  as opposed to autosomal chromosomes  first discovered by T.H. Morgan at Columbia U.  Drosophila breeding  good genetic subject  prolific  2 week generations  4 pairs of chromosomes  XX=female, XY=maleAP Biology
    • 16. Classes of chromosomes autosomal chromosomes sex chromosomesAP Biology
    • 17. Discovery of sex linkage true-breeding true-breeding XP red-eye female white-eye male Huh! Sex matters?! 100%F1 red eye offspringgeneration(hybrids) 100% 50% red-eye male red-eye female 50% white eye maleF2generationAP Biology
    • 18. What’s up with Morgan’s flies? x x RR rr Rr Rr r r R r R Rr Rr R RR Rr Doesn’t work that way! R Rr Rr r Rr rrAP Biology 100% red eyes 3 red : 1 white
    • 19. Genetics of Sex  In humans & other mammals, there are 2 sex chromosomes: X & Y  2 X chromosomes  develop as a female: XX  gene redundancy, like autosomal chromosomes  an X & Y chromosome X Y  develop as a male: XY  no redundancy X XX XY X XX XYAP Biology 50% female : 50% male
    • 20. Let’s reconsider Morgan’s flies… x x XR X R XrY X R Xr XR Y Xr Y XR Y XR XR XR Xr XR Y XR X R XR Y BINGO! XR Xr XR Xr XR Y XR Xr XrY 100% red femalesAP Biology 100% red eyes 50% red males; 50% white males
    • 21. Genes on sex chromosomes  Y chromosome  few genes other than SRY  sex-determining region  master regulator for maleness  turns on genes for production of male hormones  many effects = pleiotropy!  X chromosome  other genes/traits beyond sex determination  mutations:  hemophilia  Duchenne muscular dystrophyAP Biology  color-blindness
    • 22. Ichthyosis, X-linked Placental steroid sulfatase deficiency Human X chromosome Kallmann syndrome Chondrodysplasia punctata, X-linked recessive Hypophosphatemia  Sex-linked Aicardi syndrome Duchenne muscular dystrophy Hypomagnesemia, X-linked Becker muscular dystrophy Ocular albinism Retinoschisis Chronic granulomatous disease usually Retinitis pigmentosa-3 Adrenal hypoplasia  Glycerol kinase deficiency Norrie disease Retinitis pigmentosa-2 Ornithine transcarbamylase means deficiency Incontinentia pigmenti Wiskott-Aldrich syndrome “X-linked” Menkes syndrome Androgen insensitivity Sideroblastic anemia Charcot-Marie-Tooth neuropathy  more than Aarskog-Scott syndrome PGK deficiency hemolytic anemia Choroideremia Cleft palate, X-linked Spastic paraplegia, X-linked, 60 diseases Anhidrotic ectodermal dysplasia uncomplicated Deafness with stapes fixation Agammaglobulinemia Kennedy disease PRPS-related gout traced to Pelizaeus-Merzbacher disease Alport syndrome Lowe syndrome Lesch-Nyhan syndrome genes on X Fabry disease HPRT-related gout Immunodeficiency, X-linked, Hunter syndrome with hyper IgM Hemophilia B chromosome Lymphoproliferative syndrome Hemophilia A G6PD deficiency: favism Drug-sensitive anemia Albinism-deafness syndrome Chronic hemolytic anemia Manic-depressive illness, X-linked Fragile-X syndrome Colorblindness, (several forms) Dyskeratosis congenita TKCR syndrome Adrenoleukodystrophy Adrenomyeloneuropathy Emery-Dreifuss muscular dystrophyAP Biology Diabetes insipidus, renal Myotubular myopathy, X-linked
    • 23. Map of Human Y chromosome? < 30 genes on Y chromosome Sex-determining Region Y (SRY) Channel Flipping (FLP) Catching & Throwing (BLZ-1) Self confidence (BLZ-2) note: not linked to ability gene Devotion to sports (BUD-E) Addiction to death & destruction movies (SAW-2) Air guitar (RIF) Scratching (ITCH-E) Spitting (P2E) linked Inability to express affection over phone (ME-2) Selective hearing loss (HUH) Total lack of recall for dates (OOPS)AP Biology
    • 24. AP Biology
    • 25. sex-linked recessive Hemophilia XHhh x XHY H X HH XH male / sperm XH X h XH Y Xh X HY female / eggs X H XH X H XH X HY Xh X H Xh Xh Y YAP Biology carrier disease
    • 26. X-inactivation  Female mammals inherit 2 X chromosomes  one X becomes inactivated during embryonic development  condenses into compact object = Barr body  which X becomes Barr body is random  patchwork trait = “mosaic” patches of black XH  XH X htricolor cats Xhcan only befemale AP Biology patches of orange
    • 27. Male pattern baldness  Sex influenced trait  autosomal trait influenced by sex hormones  age effect as well = onset after 30 years old  dominant in males & recessive in females  B_ = bald in males; bb = bald in femalesAP Biology
    • 28. Environmental effects  Phenotype is controlled by both environment & genes Human skin color is influenced by both genetics & environmental conditions Coat color in arctic fox influenced by heat sensitive allelesColor of Hydrangea flowers AP Biologyis influenced by soil pH
    • 29. Any Questions?AP Biology 2006-2007

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