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C-13 Part II Non-Mendelian inheritance

C-13 Part II Non-Mendelian inheritance. Most phenotypes reflect the influences of several to many genes and by the environment. Continuous variation. When multiple genes act together to produce a physical (phenotypic) character, a gradation or range of differences occur.

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C-13 Part II Non-Mendelian inheritance

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  1. C-13 Part IINon-Mendelian inheritance Most phenotypes reflect the influences of several to many genes and by the environment

  2. Continuous variation • When multiple genes act together to produce a physical (phenotypic) character, a gradation or range of differences occur. • Examples: height, weight in humans • Referred to as polygenic traits

  3. Pleiotropic effects • Occurs when an allele has >1 effect on phenotype • Examples are: • Sickle cell anemia • Cystic fibrosis

  4. Incomplete dominance • Situation where 2 alleles “blend” to form hybridized phenotype • Examples: • Flower color in 4 o’clocks and snapdragons

  5. Environmental effects • Allele expression may be affected by environmental conditions • Examples: • Coat color in arctic foxes • Coat color in Himalayan rabbits and Siamese cats • ch allele affected by temp >33 C  tyrosinase enzyme inactivates + reduces melanin pigment production

  6. Epistasis – genes acting “in concert” • Situation whereby 1 gene pair affects the expression of a 2nd gene pair • Examples: • Anthocyanin (purple) pigment in corn • Animal coat colors

  7. Epistasis (cont’d) • Horse coloration involves 2 or more gene pairings.. • EE or Ee is for black • ee is for red (sorrel) • PLUS other genes can add to base colors • (Bay is AA, EE – black with agouti gene; Buckskin is AA, EE, CcrC – bay with cremello gene, Dun is AA, EE, Dd – bay with dun gene; Palomino is ee, CcrC – sorrel with cremello gene)

  8. Mutation of genes causes genetic disorders • Most gene disorders are RARE – nonadaptive • Most are recessively inherited: • Tay Sachs disease Sickle cell anemia • Some disorders are inherited in a dominant fashion: • Huntington’s disease

  9. Multiple alleles and Blood Groups • ABO Blood groups • IAIA and Iai = type A • IBIB and IBi = Type B • IAIB and IBIA = Type AB • ii = Type O • Rh blood factor • Rh + • Rh-

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