I\'m having difficulty understanding part (B) of this problem. Please explain yo

Question

I'm having difficulty understanding part (B) of this problem. Please explain your answer thoroughly (don't just give me the answer)

Assume that a female fly that has disrupted wings (dsr) and a speck body (sp) is mated to a male that has cinnabar eyes (cn) Part B Phenotypically wild-type F1 female progeny were mated to males that had speck bodies, disrupted wings and cinnabar eyes, and the following progeny were observed With respect to the three genes mentioned in the problem, what are the genotypes of the parents used in making the phenotypically wild-type F1 heterozygote? Phenotype wild-type disrupted wings speck body cinnabar eyes Number of offspring 112 52 sp dsrcn sp dsrcn and sp dsr cnspdsr cn sp dsr cn sp dsr cn and sp dsr onsp dsr on 235 disrupted wing speck body 241 Submit disrupted wings, cinnabar eyes 25 speck body. cinnabar eyes 46 Part C disrupted wings speck body. cinnabar eyes What is the map distance between sp and dsr? Express your answer to the nearest whole number

Explanation / Answer

Answer: sp dsr cn+/ sp dsr cn+ andsp+ dsr+ cn/ sp+ dsr+ cn

Explanation:

Hint: High number progeny are the parental progeny. So, cinnabar phenotype is on one chromosome and disrupted wings, speck body phenotypes are on the homologous chromosome. Therefore its genotype would be sp+ dsr+ cn / sp dsr cn+. Male would have acted as tester parent and its genotype would be sp dsr cn / sp dsr cn.

The female genotype is sp+ dsr+ cn / sp dsr cn+ means that “sp+ dsr+ cn” gamete came from one parent and “sp dsr cn+” gamete is from other parent. Finally, one parental genotype would be sp+ dsr+ cn/ sp+ dsr+ cn and another parental genotype is sp dsr cn+/ sp dsr cn+

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