GENETICS QUESTION!! When Freddy the fly, who has big eyes (the mutant phenotype)

Question

GENETICS QUESTION!!
When Freddy the fly, who has big eyes (the mutant phenotype), mates with Fredonia the fly, who has small eyes, their offspring appear in the following proportions:

Note that the gene for eye size is autosomal. Fredonia is homozygous at the eye size locus. The most likely explanation for observing these proportions is:

A. The genes coding for big eye size and gender appear on the same chromosome.

B. The gene coding for big eye size is X-linked recessive.

C. The gene for big eye size is autosomal dominant.

D. Fredonia doesn't like Freddy.

E. The gene coding for big eye size is autosomal recessive trait.

Table 1. Offspring phenotypes with proportions Phenotype Proportion Big-eyes, female 25% Small-eyes, female 25% Big-eyes, male 25% Small-eyes, male 25%

Explanation / Answer

Answer:

C. The gene for big eye size is autosomal dominant.

Explanation:

Big eyes is dominant and its allele is B.

Small eyes is recessive and its allele is b.

(Big eye) Bb x bb (small eye)----Parents

50% big eyes (25% male + 25% female) : 50% small eyes (25% male + 25% female)

b B Bb (big eyes) b bb (small eyes)

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