In the pathway depicted below, pigment molecules are created through chemical re

Question

In the pathway depicted below, pigment molecules are created through chemical reactions catalyzed by the various enzymes, encoded by their respective genes. The white pigments do not affect color. Pigments can combine to create new colors (orange and purple). Each enzyme has a dominant allele and recessive allele. Genes A – D, when at least one wild type allele is present, catalyze their respective reactions. The intermediate molecules (yellow and red) are completely converted into products if the enzyme is present. Enzyme D can convert red pigment into yellow pigment, when at least one wild type allele is present. Gene E is a dominant inhibitor of enzyme B; when at least one dominant allele of E is present, the B enzyme will not function. What genotypes would you cross to achieve the following phenotypic ratios? Some questions have multiple possible answers.

A. 9 blue: 3 yellow: 4 white

B. 9 purple: 3 orange: 3 blue: 1 yellow

C. 15 yellow: 1 white

D. 13 yellow: 3 blue

E. 9 orange: 3 red: 3 yellow: 1 white

F. 12 yellow: 4 red

Explanation / Answer

Genotype AaBbCcDdEe will be used to achieve such ratio.

Total genotypes 25 x 25 = 625 because AaBbCcDdEe; 5 alleles will make 52 gametes for each parent. This will always give phenotype ratio as 9:3:3:1 ratio

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