EX 3.28 color of pea seed

The color of pea seeds is determined by a single genetic locus.

• If the two alleles at this locus are AA or Aa (the genotype), then the pea will be yellow (the phenotype)
• if the allele is aa, the pea will be green.

Suppose we

• pair off 20 Aa seeds
• cross the two seeds in each of the ten pairs to obtain ten new genotypes.

Call each new genotype

• a success $S$ if it is aa
• a failure otherwise.

Then with this identification of $S$ and $F$ , the experiment is binomial with

• $n=10$
• $p=P(\text{aa genotype})$.

If each member of the pair is equally likely to contribute a or A, then $p=P\left(a\right)\cdot P\left(a\right)=\left(.5\right)\left(.5\right)=.25$