Scalloped sd wing is an Xlinked recessive and ebony e body c

Scalloped (sd) wing is an X-linked recessive and ebony (e) body color is an autosomal recessive mutation in Drosophila. If a true breeding scalloped female which is wild type for ebony is mated with a true breeding male mutant only for ebony, what proportion of scalloped, normal body colored males is expected in the F2?

0

1/8

1/16

1/32

3/16

--------------------------------------------------------------------------------------------------------------------------------------------------------------

Vitamin D-resistant rickets is an X-linked dominant disorder. Red hair is an autosomal recessive trait. Mary has rickets, which she inherited from her father, her mother does not have the disorder. Mary also has red hair. Her husband Tom does not have rickets or red hair, but his mother had red hair. What is the chance that a child of Mary and Tom will be a boy that has both rickets and red hair?

none

1/8

1/16

3/8

1/4

Solution

Scalloped =sd, ebony =sd^-

Female XX +AA        x               AA^- +X0 Male [0= no extra chromosome] [Parents]

Gametes

Female (Downside)

Male (right side)

X + A

XX + A A^-

X0 + AA^-

            [F1 progenies]

The trait is autosomal recessive mutation which require autosome chromosome. The female does not have the trait so her autosome chromosome is free of the trait. Now the male should has two alleles of the trait to be diseased. So progenies will not get diseased.

The option 1^st is correct.

Mary has rickets [X⁰] which is inherited from her father. Daughter gets X chromosome from father. Mary has red hair so her autosomal chromosome has aa genotype [a here represent recessive allele]. Tom does not have rickets or red hair but his mother has so she also has aa genotype. Tom should have Aa genotype.

So Mary X⁰X +aa                    x           Aa + XY

The cross to find boy

Gametes

Female (Downside)

Male (right side)

Y +A

Y + a

X + a

XY + Aa

XY + aa

X⁰ + a

X⁰Y + Aa

X⁰ Y +aa [both rickets and red hair

So there are 1 in 4 possibilities that the boy has both rickets and red hair.

The option e is correct.