Question

Anthocyanins are a class of red to purple plant pigments that are ph sensitive and can sometimes accumulate to high levels in plant tissues causing darker color phenotypes. Two varieties of tomatoes, one with red fruit and one with dark purple fruit, that have mutant alleles at different genes are crossed. Which biochemical pathway phenotype pattern is most consistent with the following dihybrid F2 pigment phenotype observations? In the possible answers below the phenotype resulting from the pathway stopping at that point is given in parentheses. The arrows indicate the action of gene products (each arrow corresponds to a single and different gene product in the biosynthesis step). A) (red) rightarrow (purple) rightarrow (red) B) (purple) rightarrow (red) rightarrow (purple) C) (purple) rightarrow (red); (purple) rightarrow (red) D) (purple) rightarrow (purple) rightarrow (red) E) (red) rightarrow (red) rightarrow (purple)

Answer 1

purple tomatoes are pigmented by a large amount of lycopene and lesser amounts of beta-carotene, driven by the 'red' ('R') gene, as well as by chlorophyll from the 'green-flesh' ('gf') gene. The skin of these tomatoes is clear driven by the mutant allele ('y') of the 'yellow' gene.

red tomato is pigmented by a large amount of lycopene and lesser amounts of beta-carotene, driven by the 'red' ('R') gene. The skin of these tomatoes also has a yellow pigment driven by the 'yellow' ('Y') gene.