(version 22 August 2005)
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If we have three loci, how do we order them?
sc (scute = bristles), ec (echinus, eye shape mutant), vg (vestigal wing).
sc+ , ec+, vg+ are dominant alleles
vermilion (v), crossveinless (cv), cut (ct)
v+, cv+, ct+ are dominant
Cross v+ cv ct / v cv+ ct+ to a v cv ct / v cv ct triple-recessive testcross strain. Let RF(A,B) denote the recombination frequency (or fraction) between loci A and B.
Parents are v+ cv ct / v cv+ ct+
rarest class ( v cv+ ct, v+ cv ct+ ) = double recombinants
Which gene order gives these as double recombinants?
Presence of one crossover may influence the probability of nearby crossovers
First, what is the expected recombination fraction if no interfence?
If no interference, Pr(double recomb) = c1 * c2