Chapter 25, Problem 6PDQ

An inbred strain of plants has a mean height of 24 cm. A second strain of the same species from a different geographic region also has a mean height of 24 cm. When plants from the two strains are crossed together, the F₁ plants are the same height as the parent plants. However, the F₂ generation shows a wide range of heights; the majority are like the P₁ and F₁ plants, but approximately 4 of 1000 are only 12 cm high and about 4 of 1000 are 36 cm high.

1. (a) What mode of inheritance is occurring here?
2. (b) How many gene pairs are involved?
3. (c) How much does each gene contribute to plant height?
4. (d) Indicate one possible set of genotypes for the original P₁ parents and the F₁ plants that could account for these results.
5. (e) Indicate three possible genotypes that could account for F₂ plants that are 18 cm high and three that account for F₂ plants that are 33 cm high.