Two different antigen molecules that occur on the surface of blood cells of wild

Question

Two different antigen molecules that occur on the surface of blood cells of wild-type mice are produced through this biosynthetic pathway.

Mice that are homozygous for null mutations in the gene that encodes enzyme A (genotype aa) don't make either antigen 1 or antigen 2. Mice that are homozygous for null mutations in the gene that encodes enzyme B (genotype bb) don't make antigen 1. Mice that are homozygous for null mutations in the gene that encodes enzyme C (genotype cc) don't make antigen 2. All three genes are unlinked.

Two different antigen molecules that occur on the surface of blood cells of wild-type mice are produced through this biosynthetic pathway.

Mice that are homozygous for null mutations in the gene that encodes enzyme A (genotype aa) don't make either antigen 1 or antigen 2. Mice that are homozygous for null mutations in the gene that encodes enzyme B (genotype bb) don't make antigen 1. Mice that are homozygous for null mutations in the gene that encodes enzyme C (genotype cc) don't make antigen 2. All three genes are unlinked.

Two different true-breeding strains of mice have been isolated that don’t make either antigen 1 or antigen 2. When an individual from one strain is crossed with an individual from the other strain, all of the F1 mice produce both antigens.

Part A

What are the complete genotypes of the two parental strains?

?AABBCC

?AAbbCC

?AABBcc

?AAbbcc

?aaBBCC

?aaBBcc

?aabbCC

?Aabbcc

Part B Two of the F1 mice are crossed to one another. What proportion of the F2 progeny will produce both antigen 1 and antigen 2? Enter your answer as a fraction.

Part C If F1 mice are crossed to one another, what proportion of the F2 progeny would be expected to produce antigen 1, but not antigen 2?Enter your answer as a fraction.

Part D If F1 mice are crossed to one another, what proportion of the F2 progeny would be expected to produce antigen 2, but not antigen 1? Enter your answer as a fraction.

Part E If F1 mice are crossed to one another, what proportion of the F2 progeny would be expected to produce neither antigen 1 nor antigen 2?Enter your answer as a fraction.

Part F Among the F2 progeny, there will be mice of several different genotypes that are phenotypically antigen 1– and antigen 2–. If you wanted to use a testcross in order to test whether any individual F2 mouse that doesn’t produce either antigen is defective in the production of enzyme A, what would be the best genotype for the tester mouse? List the gene in your answer in alphabetical order with no spaces between them. For example: DDEEFF, DdEdFf, ddeeff, etc.

Explanation / Answer

What are the complete genotypes of the two parental strains?

AaBBcc    x AabbCC                 

AaBBcc :here Aa produces antigen 1 or 2 , where as cc suppresses antigen 2, so antigen 1 is expressed. because of BB genotype.         

AabbCC    : Aa produces antigen 1 or 2 , where as bb suppress antigen 1, so antigen 2 is expressed because of genotype CC.

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