Polygenic Inheritance.pdf - Ellie zenebe Name Date Unit 7...

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Name________________________________________ Date_______ Unit 7: Polygenic Inheritance Exercise 10 Differences in skin color are largely due to differences in the amount of melanin, a dark pigment produced by skin cells. At least three genes control the synthesis of melanin.  Each gene has two forms:  an allele for high melanin production, or dark skin (A,B,C), and an allele for low melanin production, or light skin (a,b,c).  Each dark skin allele (A,B,C) in the genotype adds a small but equal amount of pigment to the skin.  There are seven different shades of skin color ranging from very dark (AABBCC) to very light (aabbcc).  Most individuals produce a medium amount of melanin and are of intermediate skin color (AaBbCc). The following Punnett square shows the possible offspring from a cross between two individuals of intermediate skin color. AaBbCc X AaBbCc Gametes ABC ABc AbC Abc aBC aBc abC abc ABC AABBCC AABBCc AABbCC AABbCc AaBBCC AaBBCc AaBbCC AaBbCc ABc AABBCc AABBcc AABbCc AABbcc AaBBCc AaBBcc AaBbCc AaBbcc AbC AABbCC AABbCc AAbbCC AAbbCc

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