Morgan’s test-cross analysis of genetic linkage between autosomal genes

(a) Dihybrid F1 females (pr+vg+/ pr vg) are test-crossed to males homozygous for recessive mutant purple eye color and vestigial wing (pr vg/pr vg), permitting identification of progeny as carrying either a parental or a recombinant chromosome. (b) Single crossover during female meiosis leads to parental and recombinant gametes at frequencies specified by recombination or by chance, and gamete union produces test-cross progeny(a) Dihybrid F1 females (pr+vg+/ pr vg) are test-crossed to males homozygous for recessive mutant purple eye color and vestigial wing (pr vg/pr vg), permitting identification of progeny as carrying either a parental or a recombinant chromosome. (b) Single crossover during female meiosis leads to parental and recombinant gametes at frequencies specified by recombination or by chance, and gamete union produces test-cross progeny

a) vg* pr+ -. —. vg* pr‘ Red eye Fullwing R vg pr .3 =3 vg pr Purple eye Vestigial wing a'l'l X \ V9+ Pr’ V9 Pr —- can can a: vg pr vg pr Red eye Purple eye Full wing Vestigial wing vg‘ [3" V9 Pr V9 Pr' V9; Pf -. =3 “- =3 :3 m =3 V9 Pr V9 Pr V9 Pr V9 Pr Red eye Purple eye Red eye Purple eye Full wing Vestigial wing Vestigial wing Full wing 1339 1195 151 154 1339+1195_ 151+154 _ W _ 0.893 —2839 _ 0.107 Parentals Recombinants (b) F1 females F2 Observed freq uency 0.4465 Parentals 89.3% 0.4465 0.0535 Recombinants 10.7% 0.0535 1 .0000 Full-wing, red-eye Female gametes Vestigia|~wing, purple-eye test-cross males \ Gamete formation ‘ Male gametes m Expected vg pr frequency v + a Full wing ' vg pr vg pr as Purple eye 0 25 W Vestigialwing ' vg+ pr - PUFF”? eye 025 as Full wing vg pr vg pr’ - REd eye 0 25 a Vestlglal wing ' V9 pr 1 000