In Nitrovian flyti, with biological systems identical to those of earth fruit flies, there is a phenotype, Tofutti, in which the flyti are strictly vegetarian. If a true-breeding female (non-vegetarian) is mated with a vegetarian male, they produce 1000 F1 offspring in the following counts: 523 non-vegetarian female flyti; 477 non-vegetarian male flyti. In a reciprocal cross, the numbers of F1 offspring produced are: 502 non-vegetarian female flyti; 498 vegetarian male flyti. The most likely explanation for these results is:

A. The gene coding for Tofutti is X-linked dominant.

B. The gene coding for Tofutti is autosomal dominant and homozygous lethal.

C. The gene coding for Tofutti is X-linked recessive.

D. There is insufficient information to answer this question.

E. The gene coding for Tofutti is autosomal recessive and homozygous lethal.

Question

Biology

Tobias Mejia

22 June, 01:29

In Nitrovian flyti, with biological systems identical to those of earth fruit flies, there is a phenotype, Tofutti, in which the flyti are strictly vegetarian. If a true-breeding female (non-vegetarian) is mated with a vegetarian male, they produce 1000 F1 offspring in the following counts: 523 non-vegetarian female flyti; 477 non-vegetarian male flyti. In a reciprocal cross, the numbers of F1 offspring produced are: 502 non-vegetarian female flyti; 498 vegetarian male flyti. The most likely explanation for these results is:

A. The gene coding for Tofutti is X-linked dominant.

B. The gene coding for Tofutti is autosomal dominant and homozygous lethal.

C. The gene coding for Tofutti is X-linked recessive.

D. There is insufficient information to answer this question.

E. The gene coding for Tofutti is autosomal recessive and homozygous lethal.

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Answers (1)

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Elian Ayala · Answer 1

C. The gene coding for Tofutti is X-linked recessive.

Explanation:

In first cross:

non vegetarian female X vegetarian male = The entire progeny is non vegetarian.

In second cross:

vegetarian female X non vegetarian male = all females are non vegetarian and all males are vegetarian

If the gene for this trait is X-linked recessive then the above results can be explained as follows:

First cross : XTXT X XtY:

XT XT

Xt XTXt XTXt

Y XTY XTY

All males have dominant XT allele so they all will be non vegetarian. All females are heterozygous so they will also be non vegetarian.

Second cross : XtXt X XTY:

Xt Xt

XT XTXt XTXt

Y XtY XtY

All males have recessive Xt allele so they all will be vegetarian. All females have one dominant XT allele so they all will be non vegetarian.