1. Fork-line Method A method that uses genotypic ratios to predict the outcomes of genetic crosses. Based on the idea that, in a dihybrid, the two traits sort independently of one another * What happens with one trait is completely unrelated to what happens with the other trait.

2. Monohybrid Example 1 AA x Aa Allele options for 1 st parent Allele options for 2 nd parent Genotypic Ratios A ½ A ½ a ½ AA ½ Aa

3. Monohybrid Example 2 aa x Aa Allele options for 1 st parent Allele options for 2 nd parent Genotypic Ratios a ½ A ½ a ½ Aa ½ aa

4. Monohybrid Example 3 Aa x Aa Allele options for 1 st parent Allele options for 2 nd parent Genotypic Ratios ½ a ½ A ½ a ¼ AA ¼ Aa ¼ aa ½ A ½ a ½ Aa

5. Dihybrid Example 1 AABb x Aabb First, you need to do a Punnet Square for each trait in order to figure out your trait options AA Aa Bb bb Bb bb A A AaAa B b bbbb

6. Dihybrid Example 1 AABb x Aabb 1 st trait options 2 nd trait options Genotypic Ratios ½ Aa ½ Bb ½ bb ¼ AABb ¼ AAbb ¼ AaBb ¼ Aabb ½ AA ½ Bb ½ bb

7. Dihybrid Example 2 AaBB x AAbb First, you need to do a Punnet Square for each trait in order to figure out your trait options AA Aa AA Aa Bb A a AAAA B bbbb

8. Dihybrid Example 1 AABb x Aabb 1 st trait options 2 nd trait options Genotypic Ratios ½ Aa ½ Bb ½ bb ¼ AABb ¼ AAbb ¼ AaBb ¼ Aabb ½ AA ½ Bb ½ bb

9. Dihybrid Example 3 AaBb x AaBb First, you need to do a Punnet Square for each trait in order to figure out your trait options AA Aa aa BB Bb bb A a AaAa B b BbBb

10. Dihybrid Example 3 AaBB x AAbb 1 st trait options 2 nd trait options Genotypic Ratios ½ Aa ¼ BB ½ Bb ¼ bb ¼ AA ¼ aa ¼ BB ½ Bb ¼ bb ¼ BB ½ Bb ¼ bb 1/16 AABB 1/8 AABb 1/16 AAbb 1/16 aaBB 1/8 aaBb 1/16 aabb 1/8 AABB 1/4 AABb 1/8 AAbb

11. In rabbits, black fur (B) is dominant to white fur (b) and long hair (L) dominates short hair (l). What is the chance of getting a black, short- haired rabbit from a cross between a rabbit that is heterozygous for both traits and a rabbit that is white and heterozygous for long hair? B b, L l x b b, L l (first do your punnet squares) Dihybrid Example 4 Bb bb BB Bb bbbb LL Ll ll L l LlLl

12. In rabbits, black fur (B) is dominant to white fur (b) and long hair (L) dominates short hair (l). What is the chance of getting a black, short- haired rabbit from a cross between a rabbit that is heterozygous for both traits and a rabbit that is white and heterozygous for long hair? B b, L l x b b, L l Dihybrid Example 4 ½ Bb ½ bb ¼ LL ½ Ll ¼ ll ¼ LL ½ Ll ¼ ll 1/8 BbLL 1/4 BbLl 1/8 Bbll * black, short-haired 1/8 bbLL 1/4 bbLl 1/8 bbll