To determine the linkage relationship of three genes (A, B, and C) in Drosophila melanogaster, you perform a three-point testcross with a fly that is heterozygous for all three genes. The F1 progeny genotypes are:
Number of F1
a/a B/b C/c 65
A/a b/b c/c 52
a/a b/b C/c 363
A/a B/b c/c 321
a/a b/b c/c 95
A/a B/b C/c 89
a/a B/b c/c 7
A/a b/b C/c 8
Total 1,000
(a) What is the recombination frequency between loci A and B?
(b) What is the recombination frequency between loci B and C?
(c) What is the recombination frequency between loci A and C?
(d) Which gene would be located between the other two?
(e) Demonstrate the physical arrangement of the genes on the chromosome, i.e. the order of the genes on a chromosome as well as their map distances.
(f) Write out the genotypes of the parents for this cross, indicating which alleles are linked with one another for each parent?