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5.2 Dihybrid Crosses

5.2 Dihybrid Crosses. The inheritance of 2 traits at once. Dihybrid Crosses. A breeding experiment that tracks the inheritance of two traits . According to Mendel’s Law of Independent Assortment:

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5.2 Dihybrid Crosses

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  1. 5.2 Dihybrid Crosses The inheritance of 2 traits at once

  2. Dihybrid Crosses A breeding experiment that tracks the inheritance of two traits. According to Mendel’s Law of Independent Assortment: each pair of alleles segregates (separates) independently during gamete formation in metaphase I

  3. Determining the number of gametes based on genotype How many gametes will be produced for the following allele arrangements? Use this formula: 2n, where n = # of heterozygous pairs in the genotype 1. RrYy 2. AaBbCCDd 3. MmNnOoPPQQRrssTtQq

  4. Answer: 1. RrYy: 2n = 22 = 4 gametes RY Ry rY ry 2. AaBbCCDd: 2n = 23 = 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCd 3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64 gametes

  5. RY Ry rY ry x RY Ry rY ry (possible gametes produced) Dihybrid Cross Example: cross 2 individual pea plants that are heterozygous for round (Rr) and yellow (Yy) pea. R = roundRrYy x RrYy r = wrinkled Y = yellow y = green

  6. Dihybrid Cross To set up a Punnett Square for a dihybrid cross, you may need to create a much bigger grid. RY Ry rY ry RY Ry rY ry

  7. Dihybrid Cross

  8. Mendel’s 9:3:3:1 ratio A classic Mendelian example of independent assortment: The 9:3:3:1 phenotypic ratio is always associated with a dihybrid cross between 2 individuals that are heterozygous across 2 traits.

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