Question

Carrots have a gene called Fat-root with alleles F and f. F, which is dominant, encodes early development of the carrot root to make a bigger carrot faster, while f encodes later development. At an unlinked gene on the same chromosome, the dominant allele P makes purple carrots, while the absence of p makes orange roots. A true-breeding orange, skinny carrot is crossed to a true-breeding (meaning homozygous for all traits of interest) purple, fat carrot. The resulting F1 offspring are

a. true-breeding purple & fat
b. purple & fat, but heterozygous (not true-breeding)
c. 50% purple & skinny and 50% orange & fat
d. 25% of each parental and recombinant type
e. there is not enough information

Answer 1

Answer: If a true-breeding orange, skinny carrot (ppff) is crossed to a true-breeding (meaning homozygous for all traits of interest) purple, fat carrot (PPFF), the resulting F1 offspring are purple & fat, but heterozygous (not true-breeding).

Explanation: Orange-Skinny carrot (ppff) will produce only one type of gamete (pf). Likewise, purple - fat carrot (PPFF) will produce only one type of gamete (PF).

When these gametes are crossed, only one type of offspring will be produced with genotype PpFf. This implies that all offsprings in the F1 generation will be Purple and Fat but heterozygous for the traits.

Check the attached image for illustrations.