IMED2004 Study Guide - Final Guide: Drosophila Melanogaster, Genetic Distance, Zygosity
Document Summary
Recombinant chromosomes from double crossover, outer two alleles are same as in nr but middle allele is different. Provides important clue about order of genes. Progeny that result from double crossover only middle allele should differ from nr progeny. 2/4 become parental (non-recombinant) and 2 become recombinant. Just flip middle gene and now have a and b and c. Double crossover products between parental and recombinant progeny: Differences only at the middle: it is switched. Scarlet eyes (st) are recessive to red eyes (st+), ebony body colour (e) recessive to gray body colour (e+), spineless (small bristles) (ss) recessive to normal bristles (ss+). To map genes need to determine order on chr. and genetic distance between them. Set up three point testcross, cross fly heterozygous at all 3 loci and fly homozygous for recessive allele at all 3 loci. Order arbitrarily assigned at the moment until do expt.
