[Nicolas Sanchez]

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In a type of fruit fly the brown body colour allele is dominant to the black body colour allele. A male fruit fly heterozygous for body colour and a female fruit fly heterozygous for body colour were allowed to mate, producing offspring.
What is the ratio, in its simplest form, of the maximum number of genotypes in the offspring to the maximum number of phenotypes in the offspring?

A. 4 :3
B. 3 :4
C. 3 :2
D. 3 :1
E. 2 :3
F. 1 :2 :1

Discussion

[Paris]

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Since both parents are heterozygous, the offspring will have three different genotypes:

Homozygous dominant 1/4

Heterozygous 1/2

Homozygous recessive 1/4

On the other hand, we will have two phenotypes since the presence of a dominant allele makes the body colour brown.

To summarise, we have 3 possible genotypes and 2 possible phenotypes.

The answer is C.