ecture 7 Last time we discussed how to measure the distance between two genes on the x chromosome. To do this we used the trick of looking only at male progeny so the genotype of the X chromosome could be scored directly since these flies only carry one copy of the x. For autosomes, we can have the same ability to score all recombinant classes by crossing to a homozygous recessive individual. This is known as a test-cross Consider the recessive traits vestigial wings and short bristles that are specified by two different genes on the same autosome(non-sex chromosome) All F1 The F1 flies are heterozygous for both genes so we are in position to see how often crossovers between these chromosomes occur in meiosis by doing a test-cross sh (Note that the progeny sh458 have distinct phenotypes) 542 47 (crossover classes) The distance between va and sh=100x 100=10 cM 000Lecture 7 Lecture 7Lecture 7 Last time we discussed how to measure the distance between two genes on the X chromosome. To do this we used the trick of looking only at male progeny so the genotype of the X chromosome could be scored directly since these flies only carry one copy of the X. For autosomes, we can have the same ability to score all recombinant classes by crossing to a homozygous recessive individual. This is known as a test-cross. Consider the recessive traits vestigial wings and short bristles that are specified by two different genes on the same autosome (non-sex chromosome). vg sh + + O x O vg sh + + ↓ vg sh All F1: + + The F1 flies are heterozygous for both genes so we are in position to see how often
crossovers between these chromosomes occur in meiosis by doing a test-cross. O vg sh vg sh x O + + vg sh ↓ (Note that the progeny vg sh 458 have distinct phenotypes) vg sh vgsh 442 + + vg + vg sh 47 (crossover classes) +sh 53 vg sh 100 The distance between vg and sh = 100 x = 10 cM 1000