Trihybrid Cross Video Lessons

Concept

# Problem: 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).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.PhenotypeNumber of offspringwild-type112disrupted wings52speck body22cinnabar eyes235disrupted wings, speck body241disrupted wings, cinnabar eyes25speck body, cinnabar eyes46disrupted wings, speck body, cinnabar eyes117Part A. From this information, determine which gene is in the middle.a) dsrb) cnc) spPart B. 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?a) sp dsr cn / sp dsr cn and sp+ dsr+ cn+ / sp+ dsr+ cn+b) sp dsr cn+ / sp dsr cn+ and sp+ dsr+ cn+ / sp+ dsr+ cn+c) sp dsr+ cn / sp dsr+ cn and sp+ dsr+ cn / sp+ dsr+ cnd) sp dsr cn+ / sp dsr cn+ and sp+ dsr+ cn / sp+ dsr+ cnPart C. What is the map distance between sp and dsr? Express your answer to the nearest whole number.Part D. What is the map distance between dsr and cn? Express your answer to the nearest whole number.

###### FREE Expert Solution

Genotypes: The genotypes of the given phenotypes are:

• wings = dsr+, dsr (disrupted wings)

• body = sp+, sp (speck body)

• eyes = cn+, cn (cinnabar eyes)

Part A and B. Parent Generation:

Female = dsr sp cn+

Male = dsr+ sp+ cn

###### Problem Details

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).

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.

 Phenotype Number of offspring wild-type 112 disrupted wings 52 speck body 22 cinnabar eyes 235 disrupted wings, speck body 241 disrupted wings, cinnabar eyes 25 speck body, cinnabar eyes 46 disrupted wings, speck body, cinnabar eyes 117

Part A. From this information, determine which gene is in the middle.

a) dsr

b) cn

c) sp

Part B. 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?

a) sp dsr cn / sp dsr cn and sp+ dsr+ cn+ / sp+ dsr+ cn+

b) sp dsr cn+ / sp dsr cn+ and sp+ dsr+ cn+ / sp+ dsr+ cn+

c) sp dsr+ cn / sp dsr+ cn and sp+ dsr+ cn / sp+ dsr+ cn

d) sp dsr cn+ / sp dsr cn+ and sp+ dsr+ cn / sp+ dsr+ cn

Part C. What is the map distance between sp and dsr? Express your answer to the nearest whole number.

Part D. What is the map distance between dsr and cn? Express your answer to the nearest whole number.