418 Question 2.9: In the fruit fly Drosophila melanogaster, red and yellow eye p

Question

418 Question 2.9: In the fruit fly Drosophila melanogaster, red and yellow eye pigments are synthesized through the pterin pathway. These, plus the brown pigment synthesized through the ommochrome pathway, produce the dark red Drosophila eye color. A part of the pterin pathway (simplified) is shown below Red pigment Colorless Enzyme Colorless compound intermediate Yellow pigment Consider the genes encoding Enzyme 1 (et), Enzyme 2 (e2) and Enzyme 3 (e3"), respectively What are their predicted genetic interactions? A. e1 is recessively epistatic to e2, and e2 is recessively epistatic to e3. B. e1 is recessively epistatic to e3, and e3 is recessively epistatic to e2. C. e3 is recessively epistatic to e1, and e2 is recessively epistatic to e1 D. e1 is recessively epistatic to e2 and to e3. E. e2 is recessively epistatic to e1 and to e3. Question 2.10: Two unlinked mutant lines of flowering begonias have been obtained; one breeds true for yellow flower color and the other breeds true for orange flower color (wild-type flower color is scarlet). Consider the following 3 crosses yellow x scarlet Fi all scarlet-) F2 75% scarlet; 25% yellow orange x Scarlet ? F1 all scarlet ? F2 75% scarlet; 25% orange orange x yellowFi all scarletF2 ?? 2. 3. If the orange pigment is a precursor of the scarlet pigment, the yellow pigment is a precursor of the orange pigment, and a colorless compound is the precursor of the yellow pigment in a linear biosynthetic pathway controlling flower color, what phenotypic ratios do you expect in the F2 of cross 3? A. 3 scarlet: 1 white (colorless) B. 9 scarlet: 3 yellow:3 orange: 1 white (colorless) C. 9 scarlet: 4 yellow: 3 orange D. 9 scarlet: 7 white (colorless) E. 2 scarlet: 3 yellow:1 white (colorless)

Explanation / Answer

Answer 2.9 D- e1 is respectively epistatic to e2 and e3.

Answer 2.10 E- 2 Scarlet: 3 Yellow : 1 White colourless

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