4 Two truebreeding plants with white flowers were crossed ON

4. Two true-breeding plants with white flowers were crossed. ONote: this a completely different species from the plant in Problem H1). All the F1 plants had blue flowers. An intercross between F1 plants produced the following numbers of F2 progeny 177 blue-flowered plants 142 white-flowered plants (a) Propose an explanation for the observed pattern of inheritance in flower color. Assume two independently segregating genes, A and B, are involved. Show the genotypes of F1, and plants and use the rules of probability, a Punnett Square, or a branched line diagram to find the expected genotypes and corresponding phenotypes of F2 offspring, including the expected ratios of each (4 pts)

Solution

This can be explained by a gene interaction phenomenon called Complementary gene interaction. The Biochemical path way explain this is

Colour less or white substrate--------------A --------> Colour less or white intermediate ---------B----------> Blue colour Product

Here in presence of Gene A and B (both are dominant) Blue colour appears. In all other conditions white colour appears.

The F2 ratio = 9:7 (9 = Blue, 7 = White)

Parents genotypes: AAbb (White), aaBB (White)

F1 genotype: AaBb (Blue)

F2 genotypes: If both A & B in dominant state gives blue color

All other conditions white color

Mendel ratio: 9:3:3:1 modified to 9:7 (9:3+3+1)