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When Genetics is Not Simple Other patterns of inheritance.

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Presentation on theme: "When Genetics is Not Simple Other patterns of inheritance."— Presentation transcript:

1 When Genetics is Not Simple Other patterns of inheritance

2 Its not so Simple Not all traits are controlled by single genes with simple dominant - recessive alleles: –Multiple alleles –Polygenic traits –Incomplete dominance –Codominance

3 Multiple Alleles More than two alleles exist for a particular trait (multiple flavors) –Labeled using a single letter and superscripts –Results in many possible phenotypes Ex: Human blood types I A, I B, or i

4 Polygenic Traits More than one gene controls a particular traitMore than one gene controls a particular trait –Very complicated hereditary patterns –Results in an vast array of possible phenotypes Ex: human skin, eye, and hair color

5 Incomplete dominance One allele is not completely dominant over the other –Heterozygous individuals show a trait that is an intermediate or blend of the two homozygous trait –Neither homozygous trait shows

6 Incomplete dominance –Example: Four oclock flowers RR = red flowers WW = white flowers RW = –Pink is a blend of red and white

7 Codominance –Both alleles are dominant –Both homozygous traits show in heterozygous individuals –There is no blending of traits –Results in blotches of colors

8 Codominance –Example: Feather color in chickens BB = black feathers WW = white feathers BW = –No gray! Both colors Checkered Chicken

9 Codominance –Example: Feather color in chickens BB = black feathers WW = white feathers BW = –No gray! Both colors Checkered Chicken


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