Extending Mendelian genetics. Beyond Mendel s Laws of Inheritance. Incomplete dominance. Incomplete dominance. Co-dominance. Genetics of Blood type

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1 Beyond Mendel s Lws of Inheritnce Etending Mendelin genetics Mendel worked with simple system pes re geneticlly simple most trits re controlled by single gene ech gene hs only 2 lleles, 1 of which is completely dominnt to the other The reltionship between genotype & phenotype is rrely tht simple Incomplete dominnce Heterozygote shows n intermedite, blended phenotype emple: RR = red flowers RR rr = white flowers WW Rr = pink flowers RW mke 50% less color Incomplete dominnce P F 1 genertion (hybrids) red flowers pink flowers self-pollinte white flowers 25% 50% 25% white red pink 1:2:1 RR RW WW F 2 genertion Co-dominnce 2 lleles ffect the phenotype eqully & seprtely not blended phenotype humn BO blood groups 3 lleles I, I B, i I & I B lleles re co-dominnt glycoprotein ntigens on RBC I I B = both ntigens re produced i llele recessive to both Genetics of Blood type phenotype B genotype I I or I i I B I B or I B i ntigen on RBC type ntigens on surfce type B ntigens on surfce B I I B type B ntigens on surfce both type & O i i no ntigens on surfce ntibodies in blood nti-b ntibodies nti- ntibodies no ntibodies nti- & nti-b ntibodies dontion sttus universl recipient universl donor 1

2 Pleiotropy Most genes re pleiotropic one gene ffects more thn one phenotypic chrcter 1 gene ffects more thn 1 trit dwrfism (chondroplsi) gigntism (cromegly) cromegly: ndré the Gint Inheritnce pttern of chondroplsi dominnt inheritnce dwrf dwrf lethl B_C_ bbc _cc Epistsis One gene completely msks nother gene cot color in mice = 2 seprte genes C,c: pigment (C) or no pigment (c) B,b: more pigment (blck=b) or less (brown=b) cc = lbino, no mtter B llele 9:3:3:1 becomes 9:3:4 50% dwrf:50% norml or 1:1 67% dwrf:33% norml or 2:1 Epistsis in Lbrdor retrievers 2 genes: (E,e) & (B,b) pigment (E) or no pigment (e) pigment concentrtion: blck (B) to brown (b) eebb eeb E bb E B Polygenic inheritnce Some phenotypes determined by dditive effects of 2 or more genes on single chrcter phenotypes on continuum humn trits skin color height weight intelligence behviors 2

3 Skin color: lbinism However lbinism cn be inherited s single gene trit = lbino lbino fricns Johnny & Edgr Winter Se linked trits Genes re on se chromosomes s opposed to utosoml chromosomes first discovered by T.H. Morgn t Columbi U. Drosophil breeding good genetic subject prolific 2 week genertions 4 pirs of chromosomes =femle, =mle melnin = universl brown color enzyme tyrosine melnin lbinism Clsses of chromosomes utosoml chromosomes P Discovery of se linkge F 1 genertion (hybrids) red-eye femle red eye offspring white-eye mle se chromosomes F 2 genertion red-eye femle 50% red-eye mle 50% white eye mle Wht s up with Morgn s flies? RR rr Rr Rr r r R r R Rr Rr R RR Rr Doesn t work tht wy! R Rr Rr r Rr rr red eyes 3 red : 1 white Genetics of Se In humns & other mmmls, there re 2 se chromosomes: & 2 chromosomes develop s femle: gene redundncy, like utosoml chromosomes n & chromosome develop s mle: no redundncy 50% femle : 50% mle 3

4 femle / eggs Let s reconsider Morgn s flies R R R R r R r R r r R R red eyes R r R r R R R R r R R r red femles 50% red mles; 50% white mles Genes on se chromosomes chromosome few genes other thn SR se-determining region mster regultor for mleness turns on genes for production of mle hormones mny effects = pleiotropy! chromosome other genes/trits beyond se determintion muttions: hemophili Duchenne musculr dystrophy color-blindness Humn chromosome Se-linked usully mens -linked more thn 60 diseses trced to genes on chromosome Duchenne musculr dystrophy Becker musculr dystrophy Chronic grnulomtous disese Retinitis pigmentos-3 Norrie disese Retinitis pigmentos-2 Sideroblstic nemi rskog-scott syndrome PGK deficiency hemolytic nemi nhidrotic ectoderml dysplsi gmmglobulinemi Kennedy disese Pelizeus-Merzbcher disese lport syndrome Fbry disese Immunodeficiency, -linked, with hyper IgM Lymphoprolifertive syndrome lbinism-defness syndrome Frgile- syndrome Ichthyosis, -linked Plcentl steroid sulftse deficiency Kllmnn syndrome Chondrodysplsi punctt, -linked recessive Hypophosphtemi icrdi syndrome Hypomgnesemi, -linked Oculr lbinism Retinoschisis drenl hypoplsi Glycerol kinse deficiency Ornithine trnscrbmylse deficiency Incontinenti pigmenti Wiskott-ldrich syndrome Menkes syndrome ndrogen insensitivity Chrcot-Mrie-Tooth neuropthy Choroideremi Cleft plte, -linked Spstic prplegi, -linked, uncomplicted Defness with stpes fition PRPS-relted gout Lowe syndrome Lesch-Nyhn syndrome HPRT-relted gout Hunter syndrome Hemophili B Hemophili G6PD deficiency: fvism Drug-sensitive nemi Chronic hemolytic nemi Mnic-depressive illness, -linked Colorblindness, (severl forms) Dyskertosis congenit TKCR syndrome drenoleukodystrophy drenomyeloneuropthy Emery-Dreifuss musculr dystrophy Dibetes insipidus, renl Myotubulr myopthy, -linked Hemophili H h Hh H h HH H mle / sperm H H H H h crrier H h disese se-linked recessive H h H H h H -inctivtion Femle mmmls inherit 2 chromosomes one becomes inctivted during embryonic development condenses into compct object = Brr body which becomes Brr body is rndom tricolor cts cn only be femle ptchwork trit = mosic ptches of blck H h H h ptches of ornge 4

5 Mle pttern bldness Se influenced trit utosoml trit influenced by se hormones ge effect s well = onset fter 30 yers old dominnt in mles & recessive in femles B_ = bld in mles; bb = bld in femles Environmentl effects Phenotype is controlled by both environment & genes Humn skin color is influenced by both genetics & environmentl conditions Cot color in rctic fo influenced by het sensitive lleles Color of Hydrnge flowers is influenced by soil ph ny Questions?