Dihybrid Cross Notes

1. Determine dominant and recessive traits Carefully read the problem

2. Assign letters for the trait B = black b = white H = Hairy h = no hair

3. Determine genotype for parents *Parents must have 4 alleles Heterozygous, black, hairless male = Bbhh White heterozygous hairy female = bbHh

4. Draw the punnett square with 16 boxes

5. Put parent gamete combinations on box Bbhh gametes: Bh, Bh, bh, bh bbHh gametes: bH, bh, bH, bh Bh Bh bh bh bH bh bH bh BbHh bbHh Bbhh bbhh BbHh bbHh Bbhh bbhh

Extra tips When determining the probability of events –If the problem states and then multiply the chances for each Chance of heads and heads = ½ x ½ = ¼ or 25% –If the problem states or then add the chances for each Chance of heads or tails = ½ + ½ = 1 or 100% As you work the problems write in your own extra tips