1. (two traits)

2. A dihybrid cross is a cross among two traits.
Example: Show the possible combinations of offspring of a dog who is heterzygous for both black fur and curly hair and another dog who is recessive for yellow and straight fur.
Dihybrid Punnett squares are prediction tools used to determine probability for two traits.

3. 1) Determine parental genotypes.
2) Determine possible combinations among alleles for each gene when forming gametes. 
*Remember, you only inherit one allele per gene from each parent* BC bc Bc bC bc

4. bc bc bc bc BC 4/ of 16 or 25% Bc bC 4/ of 16 or 25% bc
Which percentage of offspring can be predicted to have Black fur (B)  AND Curly hair (C)? BC
BbCc
BbCc
BbCc
BbCc
4/ of 16 or 25% Bc
Bbcc
Bbcc
Bbcc
Bbcc
Which percentage of offspring can be predicted to have Black fur (B)  AND straight hair (c)? bC
bbCc
bbCc
bbCc
bbCc
4/ of 16 or 25% bc
bbcc
bbcc
bbcc
bbcc

5. bc bc bc bc BC 4/ of 16 or 25% Bc bC 4/ of 16 or 25% bc
Which percentage of offspring can be predicted to have yellow fur (b)  AND Curly hair (C)? BC
BbCc
BbCc
BbCc
BbCc
4/ of 16 or 25% Bc
Bbcc
Bbcc
Bbcc
Bbcc
Which percentage of offspring can be predicted to have Yellow fur (b)  AND straight hair (c)? bC
bbCc
bbCc
bbCc
bbCc
4/ of 16 or 25% bc
bbcc
bbcc
bbcc
bbcc

6. When crossing 2 heterzygotes (Aa x Aa)
Remember the 3:1 ratio from our monohybrid squares?
dominant : recessive

7. There is a similar pattern when we create a dihybrid cross for two individuals who are heterozygous for both traits!

8. 9 Short-tailed Brown cats
Ex) Crossing two short-tailed brown cats that are both  heterozygous for each trait
9 Short-tailed Brown cats
3 Short-tailed white cats
3 long-tailed brown cats
1 long-tailed white cat

9. Cross two heterozygous individuals.
In guinea pigs, short hair (S) is dominant over long hair (s); and black fur (B) is dominant to white fur (b). 
Cross two heterozygous individuals.   SB Sb sB sb SB Sb sB sb