this is all of the information that I have please help Lab 5 Introduction - Genetic mapping See figure 5.1 for a schematic of the fly the cross you initially started with, you'll either crosses you have been working on. Two labs ago, map the distance between the w gene and the m you set up a pair of reciprocal parental crosses, gene, or between the w gene and the y gene. between mutant and wild type flies (fig. 5.1a). You had one of two different mutant strains, each with two mutant phenotypes - either white eyes all F2 individuals will receive only recessive (w) and miniature wings (m), or white eyes (w) alleles from this parent (fig. 5.1d, orange and and yellow body (y). The phenotypes of the F1 yellow chromosomes). Because of this, the flies should have indicated to you that all mutant phenotype of each F2 fly will tell you which phenotypes in question are x- linked recessive alleles (mutant or WT) were inherited from the (fig. 5.1b). heterozygous female F1 parent (fig. 5.1d, dark and light blue chromosomes). The first F2 fly Last lab, you used the F1 flies from one of shown in figure 5.1d inherited 'a B' from the your parental crosses to set up an F1 cross (fig. heterozygous parent and will end up with the consequence. After crossing two pure breeding this F2, you observe a ABphenotype and parents, F1 offspring will be heterozygous for therefore know that this fly received 'A B' from nearly all genes in question - the exception is X - the heterozygous parent. linked genes in the male offspring. Since the Y chromosome is equivalent to recessive alleles for The goal of genetic mapping is to X-linked genes, these F1 males are recessive for determine the likelihood of cross over between all X-linked genes and act as a test cross. The two loci/genes. If we score the phenotypes of a heterozygous F1 females and recessive F1 males large F2 population from our crosses, we can (test cross) can be used to map the distance determine the recombination frequency of your between the genes causing the two phenotypes two genes. of your parental mutant female. Depending on e) F2 phenotype scoring: f) Recombination frequency: Eigure 5.1: Schematic of your Drosophila crosses, See text of lab 5 intro for description. For a given F1 gamete for the F2 individual it number of flies, it is easy to calculate the creates), if no cross over occurs between the two recombinant frequency between your two genes genes in question, the F2 phenotype will be the (fig. 5.1ef ). same as one of the original parents - either fully WT or double mutant in this case. In figure 5.1d Recall from last time that a lower recombinant these have blue chromosomes of a single colour. frequency is observed when genetic map If a crossover does occur between the two genes, distances are small. When genes are close to the F2 fly will have a phenotype unlike either of each other, there's a narrow range on the the parents - a recombinant phenotype (shown chromosome for a random crossover to land.