Question 1 Pigment in the mouse is only produced when the C allele is present. I

Question

Question 1

Pigment in the mouse is only produced when the C allele is present. Individuals of thecc genotype have no color. If color is present, it may be determined by the A and aalleles. AA or Aa results in agouti color, while aa results in black coats.

(a) What F1 and F2 genotypic and phenotypic ratios are obtained from a crossbetween AACC and aacc mice?

(b) In three crosses between agouti females whose genotypes were unknown andmales of the aacc genotype, the following phenotypic ratios were obtained:

(1) 8 agouti, 8 colorless

(2) 9 agouti, 10 black

(3) 4 agouti, 5 black, 10 colorless

What are the genotypes of the female parents in each of the three crosses?

Explanation / Answer

(a) The F1 are all Aa Cc (agouti) (color can be expressed) The F2 are 9/16 A- C- (agouti), 3/16 A- cc (albino), 3/16 aa C- (black), 1/16 aa cc (albino), so 9/16 are agouti, 3/16 black, and 4/16 albino

(b) since half of the offspring are albino, the female must have been Cc, and since half of the pigmented offspring are black and half are agouti, she must have been Aa hence her genotype is Aa Cc.

AC Ac aC ac AC AACC AACc AaCC AaCc Ac AACc AAcc AaCc Aacc aC aACc aACc aaCC aaCc ac aAcC aAcc aacC aacc

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