Incomplete Dominance Co-dominance

Click here to load reader

download Incomplete Dominance Co-dominance

of 17

  • date post

    02-Jan-2016
  • Category

    Documents

  • view

    31
  • download

    0

Embed Size (px)

description

Incomplete Dominance Co-dominance. 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 - PowerPoint PPT Presentation

Transcript of Incomplete Dominance Co-dominance

Chapter 14.

Bi 2g, 3aIncomplete DominanceCo-dominance1Extending Mendelian geneticsMendel worked with a simple systempeas are genetically simplemost traits are controlled by a single geneeach gene has only 2 alleles, 1 of which is completely dominant to the otherThe relationship between genotype & phenotype is rarely that simple

2Incomplete dominanceHeterozygote shows an intermediate, blended phenotypeexample:RR = red flowersrr = white flowersRr = pink flowersmake 50% less color

RRRRWWRWWWRW3

Incomplete dominancetrue-breedingred flowerstrue-breeding white flowersXP100%100% pink flowersF1generation(hybrids)

self-pollinate

25%whiteF2generation

25%red1:2:150%pink

Its likeflipping 2 pennies! 4

Co-dominance2 alleles affect the phenotype equally & separatelynot blended phenotypehuman ABO blood groups3 allelesIA, IB, iIA & IB alleles are co-dominantglycoprotein antigens on RBCIAIB = both antigens are producedi allele recessive to both

5Genetics of Blood typepheno-typegenotypeantigenon RBCantibodiesin blooddonationstatusAIA IA or IA itype A antigenson surface of RBCanti-B antibodies__BIB IB or IB itype B antigenson surface of RBCanti-A antibodies__ABIA IBboth type A & type B antigens on surface of RBCno antibodiesuniversal recipientOi ino antigens on surface of RBCanti-A & anti-B antibodiesuniversal donor6Sex-linked InheritanceBi-2g, 3a

Sex linked traitsGenes are on sex chromosomesas opposed to autosomal chromosomesfirst discovered by T.H. Morgan at Columbia U.Drosophila breedinggood genetic subjectprolific2 week generations4 pairs of chromosomesXX=female, XY=male

1910 | 1933

8

Huh!Sex matters?!F2generation100%red-eye female50% red-eye male50% white eye maleDiscovery of sex linkagePXF1generation(hybrids)100%red eye offspring

true-breeding white-eye male

true-breedingred-eye female

9Genetics of SexIn humans & other mammals, there are 2 sex chromosomes: X & Y2 X chromosomesdevelop as a female: XXgene redundancy,like autosomal chromosomesan X & Y chromosomedevelop as a male: XYno redundancy

XYXXXXXYXY50% female : 50% maleXX

10XRXRXrYSex-linked inheritancex

XrYXR100% red eyes

XR

XRXrXRYXRYXRXrx

XRXrXRYXRYXRXr

XRXrXRYXRXR

XrY100% red females50% red males; 50% white malesBINGO! 11Human X chromosomeSex-linkedusually meansX-linkedmore than 60 diseases traced to genes on X chromosome

Duchenne muscular dystrophyBecker muscular dystrophyIchthyosis, X-linkedPlacental steroid sulfatase deficiencyKallmann syndromeChondrodysplasia punctata, X-linked recessiveHypophosphatemiaAicardi syndromeHypomagnesemia, X-linkedOcular albinismRetinoschisisAdrenal hypoplasiaGlycerol kinase deficiencyIncontinentia pigmentiWiskott-Aldrich syndromeMenkes syndromeCharcot-Marie-Tooth neuropathyChoroideremiaCleft palate, X-linkedSpastic paraplegia, X-linked, uncomplicatedDeafness with stapes fixationPRPS-related goutLowe syndromeLesch-Nyhan syndromeHPRT-related goutHunter syndromeHemophilia BHemophilia AG6PD deficiency: favismDrug-sensitive anemiaChronic hemolytic anemiaManic-depressive illness, X-linkedColorblindness, (several forms)Dyskeratosis congenitaTKCR syndromeAdrenoleukodystrophyAdrenomyeloneuropathyEmery-Dreifuss muscular dystrophyDiabetes insipidus, renalMyotubular myopathy, X-linkedAndrogen insensitivityChronic granulomatous diseaseRetinitis pigmentosa-3Norrie diseaseRetinitis pigmentosa-2Sideroblastic anemiaAarskog-Scott syndromePGK deficiency hemolytic anemia

Anhidrotic ectodermal dysplasiaAgammaglobulinemiaKennedy diseasePelizaeus-Merzbacher diseaseAlport syndromeFabry diseaseAlbinism-deafness syndromeFragile-X syndromeImmunodeficiency, X-linked,with hyper IgMLymphoproliferative syndromeOrnithine transcarbamylase deficiency12

13Hemophilia 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.

HemophiliaHemophilia 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.

HemophiliaHh x HHXHYXHXhXHXhXHXhXHYYXHsex-linked recessiveXHYmale / spermXHXhfemale / eggsXHXHXHXhXHYXhYXHXHXHYXHXhXhYcarrierdisease15

X-inactivationFemale mammals inherit 2 X chromosomesone X becomes inactivated during embryonic developmentcondenses into compact object = Barr bodywhich X becomes Barr body is randompatchwork trait = mosaic

XHXhXHXhpatches of blackpatches of orangetricolor catscan only befemale16Male pattern baldnessSex influenced traitautosomal trait influenced by sex hormonesage effect as well = onset after 30 years olddominant in males & recessive in femalesB_ = bald in males; bb = bald in females

17