In a certain species of flowering plants with a diploid genome, four enzymes are
ID: 47199 • Letter: I
Question
In a certain species of flowering plants with a diploid genome, four enzymes are involved in the generation of flower color. The genes encoding these four enzymes are on different chromosomes. The biochemical pathway involved is as follows; the figure shows that either of two different enzymes is sufficient to convert a blue pigment into a purple pigment.
white ------> green -----> blue ----> ------> purple
A true-breeding green-flowered plant is mated with a true-breeding blue-flowered plant. All of the plants in the resultant F1 generation have purple flowers. F1 plants are allowed to self-fertilize, yielding an F2 generation.
A. What are the genotypes of the P and F1 plants? Indicate which genes specify which biochemical steps. Assume that the green-flowered parent is mutant in only a single step of the pathway.
B. Determine the fraction of F2 plants with the following phenotypes: white flowers, green flowers, blue flowers, and purple flowers.
Explanation / Answer
green mutant parent with blue mutant parent yielded purple F1
A. enzyme B catalyzes white to blue, enzyme D catalyzes green to bule, enzyme C and E catalyze blue to purple.
Green plant is a mutant means mutation in enzyme B will form green and not blue.
if white: AA then green has to be:aa, Blue is :BB and Purple is aB
B. purple flowers: greenflowers: blue flowers: white flower = 9: 3:3:1