Genes a and b are 20 cM apart. An a+b+/a+b+ individual was mated with ab/ab indi
ID: 11454 • Letter: G
Question
Genes a and b are 20 cM apart. An a+b+/a+b+ individual was mated with ab/ab individual.a. Diagram the cross and show the gametes produced by each parent and the genotype of F1.
b. What gametes can the F1 produce, and in what proportions?
c. If the F1 cross was crossed to ab/ab individuals, what offspring would be expected, and in what proportion?
d. Is this an example of the coupling (cis) or the repulsion (trans) linkage phase?
e. If the F1 were intercrossed, what offspring would be expected and in what proportion?
Explanation / Answer
a+b+ /a+b+ x ab /ab
Gametes
a+b+
a+b+
ab
a+b+ /ab
a+b+ /ab
ab
a+b+ /ab
a+b+ /ab
b)
40% a+b+
,40% a b,
10% a+b,
10% a b+
(c)
F2 from testcross:
40%------------- a+b+/a b,
40% ------- a b/a b,
10%------------------- a+b/a b,
10% -------------a b+/a b
Coupling
Gametes
a+b+
a+b+
ab
a+b+ /ab
a+b+ /ab
ab
a+b+ /ab
a+b+ /ab
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