In the snail Cepaea nemoralis , an autosomal allele causing a banded shell (U) i
ID: 62916 • Letter: I
Question
In the snail Cepaea nemoralis, an autosomal allele causing a banded shell (U) is dominant to one for unbanded shell (u). A gene at a different locus determines the background color of the shell: green (B) or brown (b), with green being the dominant phenotype. A banded brown snail is crossed to an unbanded green snail; assume each parent is homozygous for these genes in the initial cross. The F1 progeny are then testcrossed.
A) What will the results of the testcross look like if these loci assort independently?
B) What will the results of the testcross look like if these loci are 38 M.U. apart?
C) What will the results of the testcross look like if these loci are 7 M.U. apart?
Explanation / Answer
A)UUbb. X uuBB
UuBb. X. uubb
UuBb , Uubb, uuBb, uubb
b)