- Rules of probability can be applied to analyze passage of single-gene traits from the parent to the offspring.

**For harder problems, where there are 2 alleles (AaBb) **

- Mutually exclusive (can’t happen at same time) = or

**Multiplication Rule**

- Two or more independent events (
*and*) - Find the probability of each individual alleles, then multiply the two by each other
__Memorize cross probabilities__**Rr x rr**= ½ Rr & ½ rr**Rr x RR**= ½ Rr & ½ RR (probability of dominant phenotype is 1)**Rr x Rr**= ¼ RR, ½ Rr & ¼ rr (probability of dominant phenotype is .75)**RR x rr**= 4/4 Rr (probability of dominant is 1)

Finding Number of Unique Gametes Given Genotype

- Aa=2, AA=1, aa= 1

Add up. Ex AaBbCCDdEE = 8