Task

In sweet pea, purple flowers appear only when two dominant genes (C and P) are both present; if either is missing, or both are recessive, flowers are white. The genes are on different chromosomes. Crossing two different homozygous white varieties (CCpp and ccPP) gave an all-purple F₁; intercrossing F₁ gave 1600 F₂ plants. 1) Briefly describe the types of interaction between non-allelic genes (complementation, epistasis, polymery). 2) Explain complementary interaction biochemically (two steps of pigment synthesis). 3) Write the P, F₁ and F₂ crosses, group the F₂ genotypes by phenotype and give the ratio. 4) Calculate the numbers of purple and white F₂ plants. 5) Find the number of plants homozygous for both genes among the white F₂ plants. 6) How many purple F₂ plants give only purple offspring when selfed? 7) What share (%) of offspring is purple if an F₁ plant is crossed with a ccpp plant? For each part, write out the law or method used (cross scheme, formulas, reasoning) and all calculations step by step.