Question

Why are the progeny of a testcross generally used to map loci? Why not the F2 progeny from an F1 × F1 cross?

a) Testcross progeny provide more accurate mapping data
b) F2 progeny have too many recombinant types
c) Testcrosses reveal the linkage phase
d) F1 × F1 crosses result in incomplete dominance

Answer 1

The progeny of a testcross are generally used to map loci because testcrosses reveal the linkage phase between two genes.

Step-by-step explanation:

The progeny of a testcross are generally used to map loci because testcrosses reveal the linkage phase between two genes. In a testcross, an organism with the dominant phenotype is crossed with an organism that is homozygous recessive. If the dominant-expressing organism is a homozygote, then all F1 offspring will be heterozygotes expressing the dominant trait. Alternatively, if the dominant expressing organism is a heterozygote, the F1 offspring will exhibit a 1:1 ratio of heterozygotes and recessive homozygotes.