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12.3 Complex inheritance in Humans

12.3 Complex inheritance in Humans. Complex inheritance. Codominance Multiple alleles Sex-linked traits Polygenic inheritance Changes in chromosome number. Codominance. Phenotypes of both homozygotes produced in the heterozygote Sickle cell anemia is an example in humans

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12.3 Complex inheritance in Humans

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  1. 12.3 Complex inheritance in Humans

  2. Complex inheritance • Codominance • Multiple alleles • Sex-linked traits • Polygenic inheritance • Changes in chromosome number

  3. Codominance • Phenotypes of both homozygotes produced in the heterozygote • Sickle cell anemia is an example in humans • Heterozygous people have both normal and sickle cells • Resistant to malaria

  4. Codominance • 1 in 12 African Americans have sickle cell anemia • Hemoglobin differs by one amino acid • Causes red blood cells to be sickle shaped • Slow blood flow, block small blood vessels

  5. Multiple alleles • More than two alleles for a trait • Human blood type • Three alleles IA, IB, I • Blood types A, AB, B, O • Match for compatibility • Identify parent

  6. Sex-linked traits • Carried on sex chromosomes • Color blindness • Hemophilia

  7. Polygenic inheritance • Traits determined by more than one gene • Often see trait as range of variation • Skin color • Eye color

  8. Changes in chromosome number • Karyotype is used to look at chromosome numbers • Unusual number of autosomes • Trisomy 21, Down syndrome • Unusual number of sex chromosomes • XO, XXX, XXY, XYY • Most lead normal lives but cannot have children, some have mental disabilities

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