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Goal #5 Polygenic Inheritance & Multiple Allele Inheritance. 1/19/12. Polygenic Inheritance. Poly = many Genic = genes The inheritance of a trait that is controlled by many genes. . Exhibit A: Human Skin Color.
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Goal #5Polygenic Inheritance&Multiple Allele Inheritance 1/19/12
Polygenic Inheritance Poly = many Genic = genes The inheritance of a trait that is controlled by many genes.
Exhibit A: Human Skin Color Approximately 5 genes are involved, creating a continuous range of skin colorations from very light to very dark, determined by number of melanin-producing alleles, where each gene has two alleles. Therefore, many genes contribute to skin color Polygenic inheritance produces this pattern. Evolution has selected for greater melanin production in areas of greater light intensity to protect against UV radiation/skin cancer, and also selected for less melanin production in lower light intensity regions to allow greater vitamin D production. The selective advantages of particular skin colors can now be overcome by the use of sun-block creams and vitamin D supplements.
A. Rh Factors 1. Rh = gene responsible for blood groups 2. Determined by two alleles: positive and negative a. Positive allele is dominant (Rh+/Rh+ or Rh+/Rh-) = Rh positive b. Negative allele is recessive (Rh-/Rh-) = Rh negative
B. ABO Blood Groups • For the trait of blood type • I is dominant – has molecules on surface • i is recessive – no molecules on surface 2. Blood type can be homo/heterozygous - II and ii are homozygous - Ii is heterozygous 3. Alleles produce antigens • IA has type A antigens • IB has type B antigens
Place a check in the boxes that correctly label donors and receivers.
Practice Problems 1. What blood types would expect the children to have if their parents are type A and type B with genotypes of IAi and IBi? 2. Could a child with type A blood have parents that have type O and type B blood?
3. What blood types would you expect the children to have if their parents are heterozygous for type A blood and type O? 4. Could a child with type B blood have parents that have type O and type A blood?