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DI-HYBRID CROSSES Unit 4 Part 2

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Di-Hybrid Crosses Genetics Problems don’t always involve only one trait. When they involve 2 traits (Ex. Corn kernel shape and corn kernel color) we call it a di-hybrid cross.

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How to Solve method #1 In Guinea pigs BLACK fur is dominant to WHITE fur and SHORT hair is dominant to LONG hair. Black (F) White (f) / Short (H) long (h)

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Method #1 – Guinea Pigs Example Problem: A heterozygous black, long haired guinea pig mates with a white, homozygous short haired guinea pig.

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How to Solve method #1 You must first write down your parental genotypes: Heterozygous black = Bb Long haired = hh White = bb Homozygous short = HH Next find the possible gamete possibilities (what will go on the outside of the punnett square) FOIL method First – Outer – Inner - Last BbhhbbHH

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How to Solve method #1 Gamete possibilities: Bh, Bh, bh, bh Gamete possibilities: bH, bH, bH, bH Bbhh x bbHH

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How to Solve method #1 Next, fill in the gamete possibilities around your LARGE punnett square. You need 16 boxes!

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How to Solve method #1 Bh Bh bh bh bH

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How to Solve method #1 Lastly, complete the genotypic and phenotypic ratios (Phenotypic is the MOST important) GR: ______BBHH ______BBHh ______ BBbb ______BbHH ______BbHh ______ Bbhh ______bbHH ______bbHh ______ bbhh PR: _____Black/Short _____Black/Long _____White/Short _____White/Long

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