DIHYBRID CROSSES Unit 4 Part 2 DiHybrid Crosses

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 A Example Problem: 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 Bbhh bb. 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

How to Solve method #1 Bbhh x bb. HH Gamete possibilities: Bh, bh, bh b. H, b. H

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 b H b H Bh bh

How to Solve method #1 Lastly, complete the genotypic and phenotypic ratios (Phenotypic is the MOST important) GR: ______BBHH ______BBHh ______ BBbb ______Bb. HH ______Bb. Hh ______ Bbhh ______bb. HH ______bb. Hh ______ bbhh PR: _____Black/Short _____Black/Long _____White/Short _____White/Long