Genes A and B are 20 cM apart. Let’s say, an Ab/Ab individual was mated with an
ID: 57382 • Letter: G
Question
Genes A and B are 20 cM apart. Let’s say, an Ab/Ab individual was mated with an aB/aB individual (This is the parental cross).
a. Write out the gamete types for each parent and the genotype of the F1.
b. Write out all the gamete that the F1 can produce, and in what proportions.
c. If the F1 individual was crossed to an ab/ab individual, what F2 offspring would be expected, and in what proportions?
d. Is this F1 an example of a coupling or repulsion dihybrid? e. If the F1 were intercrossed, what offspring would be expected and in what proportions?
Explanation / Answer
As genes A and B are 20 cM apart (means both are on thesame chromosome), cross between an Ab/Ab individual and aB/aB individual will have the offspring of 20% recombinant type and remaining 80% with parental genotype.
(a) The gametes produced by Ab/Ab individual and aB/aB are,
Ab ------> 0.4% (1/2*(1-0.8))
aB --------> 0.4% (1/2*(1-0.8))
AB -------> 1/2 (1/2*(0.2))
ab -------> 1/2 (1/2*(0.2))
Of these, Ab, aB are parental and AA, ab are recombinant.
The possible genotypes of F1 are,
The genotypes of the offspring are, 20% AaBb, 40% AAbb and 40% aaBB.
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