Biology
Animal Kingdom Solutions
Tomato flesh is typically red due to the production of lycopene, which is a carotenoid
pigment. Some tomatoes may have tangerine-colored flesh or yellow-colored flesh.
In the 1950's, researchers reported that this variation in tomato flesh color could be
explained by an epistatic interaction involving genes T and R. Previous work had
shown that red flesh is the wild-type phenotype, and that yellow flesh is caused by a
recessive mutation at the R locus only. The researchers were not sure, however, how
tangerine flesh was inherited. They established a cross between two double
heterozygous red-fleshed tomatoes and observed the following offspring: 27 red-
fleshed plants, 12 tangerine-fleshed plants, and 9 yellow-fleshed plants. Use this
information to answer the following questions.
(a) In general, what must the genotypes be for red-fleshed tomatoes, tangerine-
fleshed
tomatoes, and yellow-fleshed tomatoes, respectively?
(b) You cross a heterozygous red-fleshed plant with a true-breeding yellow-fleshed
plant. What are the genotypes of these two plants? What are the expected offspring
phenotypes, and in what proportions? Use a punnett square or product law / forked
line method to support your answer.
