We have several strains of Drosophila melanogaster that are heterozygous for sma
ID: 69272 • Letter: W
Question
We have several strains of Drosophila melanogaster that are heterozygous for small deletions in the same general region of chromosome 2. We decide to use these strains to determine the order of seven genes that we have mapped to this chromosome region. Each deletion strain is crossed to a strain with no deletion, and the table below shows which recessive alleles are expressed (observe recessive phenotype) for each cross. A) Determine the relative order of the genes. If the order of some genes cannot be determined, briefly explain why in a sentence or two (1/2 credit). B) Could the deletion strains have recessive alleles for these genes if we want to be able to interpret the results of the crosses as indicating which genes are missing from the deletion chromosome in each strain? Briefly explain (1/2 credit). A plus sign in the table indicates that the recessive phenotype was observed for that gene in some offspring of the cross. A minus sign indicates only the dominant phenotype was observed.
Deletion strainGeneN Gene OGene P | Gene Q GeneR Gene S Gene T 2 3 4 5Explanation / Answer
A) The relative order of the genes can be identified by thr presence of crosses. A gene should have atleast two crosses to determine its relativness. Here, in this case, the Gene O and Gne S have only one cross, which is hard to determine their gene relativness. There should be atleast minimum of two crosses to determine the relativness.
B) From the results, it can be interepted that all minus signs are dominant in character and cross signs are recessive.
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