Question

In a unique species of plants, flowers may be either yellow, blue, red, or mauve. A pure-breeding line with blue flowers is crossed to a pure-breeding red-flowered line, and the resulting F₁ plants have yellow flowers. In the F₂ the following ratio is observed:

9/16 yellow: 3/16 blue: 3/16 red: 1/16 mauve

If pure-breeding yellow and mauve plants are crossed, the same F₂ ratio is observed.

Give a concise genetic hypothesis for the inheritance of this trait (include number of genes, number of alleles and dominance relations between alleles).

Designate your own gene symbols and list the genotypes and ratios for each F₂ class.

Determine the expected phenotypic ratios if the F₁ from above is crossed to a pure-breeding mauve plant.

Answer 1

Epistatis:

The effect of one gene is dependent on the presence of other 2 or more genes other gene. This also results in the new phenotypic trait.

Say if the flower colour is controlled by the genes R, B dominant genes. When both dominant gene is present it gives the yellow colour. When only R gene is present gives Red, When only B gene is present gives blue, when recessive allele of r and b is present than mauve.

The type of epistatic interaction that is found is co dominance. The dominant allele has its equal expression when it is present together and produces the new trait. But when present separately each expresses its own trait.