# How does probability relate to the punnett square and the offspring?

Apr 8, 2018

each outcome listed has a 25% of happening.

#### Explanation: a punnett square takes two people with certain genotypes, and lists all the possible genotypes of their offspring.

this diagram takes the genotypes of a heterozygous mother and father. both have genotype Aa.

since each genotype has two alleles, and there are two genotypes, the number of possible outcomes is $2 \cdot 2$, which is $4$.

the probability of a certain combination of alleles in the offspring is the number of times it appears in the punnett square divided by the total number of combinations in the punnett square.

if you wanted to find the probability of an $A a$ genotype in the offspring:

number of $A a$ genotypes in punnett square: $2$

total number of possible genotypes: $4$

$\frac{2}{4} = \frac{1}{2}$

1/2 = 0.5 or 50%

the $A$$A$ and $a a$ genotypes only have a 25% chance of appearing in the offspring, since there is only one combination of alleles in the punnett square that will give $A$$A$ or $a a$.