Question

In tomato plants, the germ cells are in the flowers. The yellow (Y) gene controls flower color, such that Y_ plants have yellow flowers and yy plants have white flowers. The red (R) gene controls fruit color, such that R_ have red tomatoes and rr plants have yellow tomatoes. The R and Y genes are 15 maps unit from each other on chromosome 2. A botanist sets up a parental cross between a true breeding yellow flowered plant with red tomatoes and a plant that is true breeding, double-recessive for the Y and R genes. The gametes produced by the true-breeding plant with the dominant phenotypes is/are 1)___, while the gametes produced by the true-breeding plant with the recessive phenotypes is/are 2)___. Choose one answer. 1) YR and 2) yr 1) YR/YR and 2) yr/yr 1) YR and 2) rr 1)YR and 2) yyrr

Answer 1

***see attached pic***

You're given the phenotypes of the parents, with descriptions about their genotypes ("true breeding" = "homozygous" or "same alleles"), so it's helpful to start by writing out the genotypes of the parents.  Remember, there are two alleles for any given gene (you get one allele from each parent) and this problem is talking about 2 separate genes, so therefore our genotypes will have 2 genes x 2 alleles per gene = 4 alleles.

Once you've written the genotype, "FOIL" (first, outer, inner, last) the genotype to give you all the possible allele combinations that could be paired in that parent's gametes.

*These combinations^ will have one allele for each gene (example: YR) because the the offspring will inherit one allele for each gene from both parents when the parents' gametes come together (fertilization) for a total of two alleles for each gene.*

Your answer should be A.