A geneticist crossed pure breeding pea plants with green pods and pure breeding pea plants with yellow pods. All the offspring plants in the first generation F1 F_1\,F1 had green pods.
Explain which phenotype is dominant.
In a second cross, the green offspring plants were self-pollinated. Suggest how the geneticist made sure that all the green offspring plants were self-pollinated.
Use a genetic diagram to show the ratio of plants expected by crossing the green offspring plants. Show the parental genotypes, parental gametes, expected offspring genotypes, and expected offspring phenotypes. Use G and g to represent the alleles.
The plants actually produced in this cross were 42 green pod plants and 12 yellow pod plants. Calculate the ratio of green to yellow pod plants.
Suggest why the actual ratio of phenotypes differs from the one predicted by your genetic diagram.
A student suggested that green pods are better camouflaged from herbivores than yellow pods. Use your knowledge of natural selection to suggest how this might affect the number of green and yellow pod plants in the wild.
