You are performing experiments with Drosophila melanogaster to analyze three aut

Question

You are performing experiments with Drosophila melanogaster to analyze three autosomal, linked traits: color (brown, B), wing (normal winged, N) and antennae length (long, L). For the P generation you cross 2 true- breeding flies. The female is homozygous for both brown, wingless and the male is homozygous for both black, normal winged.

List the genotypes allele for the parents:

Show the Punnett square for the P cross:

The genotypes of the F1 generation offspring are:

You now cross an F1 female with a true-breeding black, wingless male. If you obtained 1600 F2 offspring and no recombination has occurred, the numbers of phenotypes of the offspring would be (assuming all offspring survived):

_____brown, winged               _____brown, wingless

_____black, wingless              _____black, winged

Explanation / Answer

Genotype allels of the parents will be: BBnn ( female ) and bbNN ( male)

Gametes will be : Bn and bN

CROSS

bN

BbNn

(Brown and normal wing)

BbNn

(Brown and normal wing)

BbNn

( brown and normal wing)

BbNn

(Brown and normal wing)

When f1 female is crossed with black and wingless male(bbnn)

Phenotypic ratio is 1:1:1:1

Brown winged = 1/4 ×1600= 400

Browm wingless= 1/4 × 1600= 400

Black winged = 1/4 ×1600= 400

Black wingless= 1/4 ×1600= 400

bN

BbNn

(Brown and normal wing)

BbNn

(Brown and normal wing)

BbNn

( brown and normal wing)

BbNn

(Brown and normal wing)

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