DI-HYBRID CROSSES Unit 4 Part 2. Di-Hybrid Crosses  Genetics Problems don’t always involve only one trait.  When they involve 2 traits (Ex. Corn kernel.

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DI-HYBRID CROSSES Unit 4 Part 2

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.

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)

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

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

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

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

How to Solve method #1 Bh Bh bh bh bH

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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