An inbred strain of plants has a mean height of 24 cm. A second strain of the same species from a different country also has a mean height of 24 cm. The F1 plants from a cross between these two strains are also 24 cm high. 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 4 of 1000 are 36 cm high.
(a) What mode of inheritance is occurring here?
(b) How many gene pairs are involved?
(c) How much does each gene contribute to the plant height?
(d) Indicate one possible set of genotypes of the P1 and F1 plants that could explain their heights.
(e) Indicate one possible set of genotypes to account for F2 plants that are 18 cm or 33 cm high.