12.2 Complex patterns of inheritance

Embed Size (px)


12.2 Complex patterns of inheritance. Complex patterns of inheritance. Mendel’s experiments show simple inheritance with recessive and dominant alleles Some patterns of inheritance are more complex. Complex patterns of inheritance. Incomplete dominance Codominance Multiple alleles - PowerPoint PPT Presentation

Text of 12.2 Complex patterns of inheritance

  • 12.2 Complex patterns of inheritance

  • Complex patterns of inheritanceMendels experiments show simple inheritance with recessive and dominant allelesSome patterns of inheritance are more complex

  • Complex patterns of inheritanceIncomplete dominanceCodominanceMultiple alleles Sex-linked inheritancePolygenic inheritanceEnvironmental factors

  • Incomplete dominancePhenotype of the heterozygote is in between the phenotypes of the homozygotesRR=red pigmentR1R1=white, no pigmentRR1=pink

  • CodominancePhenotypes of both homozygotes are produced in heterozygote, both alleles are expressed equallyBB=black featherWW= white featherBW= checkered

  • Multiple allelesTraits controlled by more than two allelesEach pigeon has two allelesfor feather color, but thereare many possible alleles

  • Sex-linked inheritanceIn humans have 46 chromosomes, 23 pairs22 pairs autosomesone pair sex chromosomes, determine sex

  • Sex-linked inheritanceSex-linked traits are controlled by genes located on the sex chromosomesAlleles are carried on the X chromosome, not the Y chromosome

  • Polygenic inheritanceA trait that is controlled by more than one geneGenes may be on different chromosomesEach gene may have more than one alleleTrait usually expressed in a continuous range of variability

  • Environmental factorsExternal Gene may not be expressed due to temperature, nutrition, light, chemicals, infectionFor example, this bacteriais different color when grown at different temperature

  • Environmental factorsInternalMales and females differ due to hormonesAge may change trait expression

  • Complex patterns of inheritanceMendels idea that heredity is a composite of many traits still holdsLater researchers have filled in details