The autosomal mutation Antennapedia (Antp) in Drosophia causes the antennae to d

Question

The autosomal mutation Antennapedia (Antp) in Drosophia causes the antennae to develop as if they were legs. It is dominant with respect to the visible phenotype (legs on the head), but is a recessive lethal, that is, flies that are homozygous for Antp never come out of the pupa. Given the crosses below, indicate the phenotypic ratio among surviving adult flies.

a) Antp^(+) Antp x Antp^(+) Antp

b) An antennapedia male and a normal female.

The autosomal mutation Antennapedia (Antp) in Drosophia causes the antennae to develop as if they were legs. It is dominant with respect to the visible phenotype (legs on the head), but is a recessive lethal, that is, flies that are homozygous for Antp never come out of the pupa. Given the crosses below, indicate the phenotypic ratio among surviving adult flies. a) Antp^(+) Antp x Antp^(+) Antp b) An antennapedia male and a normal female.

Explanation / Answer

Answer.

Ans. a.

Given,
Antp^(+) Antp x Antp^(+) Antp

Each Antp^(+) Antp gives gametes : Antp^(+) and Antp
Now on Cross,
Antp^(+) x   Antp^(+) = Antp^(+) Antp^(+) (Normal)
Antp^(+) x Antp = Antp^(+) Antp   (Antennapedia)
Antp x Antp^(+) = Antp^(+) Antp (Antennapedia)
Antp x Antp = Antp Antp (Recessive, Dies)

Phenotypic Ratio for Ans. a, Normal : Antennapedia = 1:2

Ans. b.

Given,
Antennapedia male and a Normal female
Genotype of ,
Antennapedia male = Antp^(+) Antp
Normal female = Antp^(+) Antp^(+)

Antp^(+) Antp gives gametes : Antp^(+) and  Antp
Antp^(+) Antp^(+) gives gametes : Antp^(+) .
On Cross,
Antp^(+) x Antp^(+) = Antp^(+) Antp^(+) (Normal)
Antp x Antp^(+) = Antp^(+) Antp (Antennapedia)

Phenotypic Ratio for Ans. b, Normal : Antennapedia = 1:1

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