PUNNETT SQUARE PROBLEMS

Simple Dominance

1. Let's say that in cats, the gene for the length of the whiskers has two alleles.  The dominant allele (W) codes for long whiskers & the recessive allele (w) codes for short whiskers.

a)  What percentage of offspring would be expected to have short whiskers from a cross between a homozygous dominant cat and a heterozygous cat?
b) If one parent cat is pure long-whiskered (WW) and the other is short-whiskered (ww), what percent of offspring would have short whiskers?

2. In purple people eaters, one-horn is dominant and no horns is recessive. Draw a Punnett Square showing the cross of a purple people-eater that is heterozygous for horns with a purple people-eater that does not have horns. Summarize the genotypes & phenotypes of the possible offspring.

3. A green-leafed luboplant is crossed with a luboplant with yellow-striped leaves (P1 generation).  The cross produces 185 green-leafed luboplants (F1 generation). Summarize the genotypes & phenotypes of the offspring that would be produced by crossing two of the green-leafed luboplants obtained in the F1 generation.

4. Mendel found that crossing wrinkle-seeded plants with pure round-seeded plants produced only round-seeded plants.  What genotypic & phenotypic ratios can be expected from a cross of a wrinkle-seeded plant & a heterozygous plant?