Na 20. In Drosophila, the the red pterin pigments, by blocking synthesis of the

Question

Na 20. In Drosophila, the the red pterin pigments, by blocking synthesis of the brown xanthommatin pigment Do eyes, while wild type xanthommatin recessive autosomal bw causes brown eyes by blocking synthesis of and the recessive sex-linked ve causes bright red (vermillion) eyes uble-mutant flies have white eyes are a dark red color, from the combination of red pterins and brown A. If a white-eyed female from a pure breeding stock carrying these mutations is mated wit a wild type male, what will be the phenotypes of the F1 males and f F1 males females B. Wha among themselves? t will be the phenotypic proportions among an F2 obtained by crossing these F1s

Explanation / Answer

Autosomal recessive - bw - Brown eyes
X linked recessive - ve - Bright red
Both recessive - bw and ve - White
Wild type bw+ ve+ = Dark red

White eye female X White type male

    bw Xve X bw+ Xve+ Y

Female - bw bw+ Xve Xve+ Wild type female
male   - bw bw+ Xve Y    Bright red

B.

Female bw bw+ Xve Xve+ X male bw bw+ Xve Y

   Gametes bw Xve bw Xve+ bw+ Xve bw+Xve+    X   bw Xve bw Y bw+ Xve bw+ Y

bw+Xve+

For females

1. bw bw Xve Xve -1 = White

2. bw Xve bw+ Xve -3 = Bright red

3. bw Xve+ bw Xve - 1 = Brown

4. bw Xve+ bw+ Xve - 3 = Dark red

For males

1. bw Xve bw Y -1 = White

2. bw Xve+ bw Y -1 = Brown

3. bw Xve bw+ Y -3 = Bright red

4. bw Xve+ bw+ Y -3 = Dark red

bw Xve bw+ Xve bw Y bw+ Y bw Xve bw bw Xve Xve bw Xve bw+ Xve bw Xve bw Y bw Xve bw+ Y bw Xve+ bw Xve+ bw Xve bw Xve+ bw+ Xve bw Xve+ bw Y bw Xve+ bw+ Y bw+ Xve bw+ Xve bw Xve bw+ Xve bw+ Xve bw+ Xve bw Y bw+ Xve bw+ Y bw+Xve+ bw+Xve+ bw Xve bw+Xve+ bw+ Xve bw+Xve+ bw Y

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