Question

A Drosophila has XXXYY sex chromosomes. All the autosomal chromosomes are normal. The sexual phenotype will be-
A. Normal female
B. Super female
C. Intersexual
D. Male

Answer 1

Hint: Drosophila is also known as the common fruit fly or vinegar fly. Drosophila flies have both X and Y chromosomes, as well as autosomes. Unlike humans, the Y chromosome does not confer maleness in them, rather, it encodes genes necessary for making sperm. Their sex is determined by the ratio of X chromosomes to autosomes.

Complete answer:
A Drosophila with XXXYY sex chromosome will be ‘Super female’.
In Drosophila, sex is primarily determined by the X: A ratio, or the ratio of the number of X chromosomes to the number of sets of autosomes. The balance between female-determining factors are encoded on the X chromosome and male-determining factors are encoded on the autosomes. Thus, XX, XXY, and XXYY flies are females, while XY and XO flies are males. According to this theory of sex determination, if the ratio of X chromosomes to the total number of sets of autosomes (X/A) is > 1, the organism will be a super female. If the ratio of X chromosome to the total number of sets of autosomes (X/A) falls between 1 and 0.50, the genotype will show an intersex phenotype. The X/A value is 1.0 for normal females and 0.5 for normal males.
The X/A ratio in the above question is absolutely greater than 1, so the organism will be Super female.

So, the correct option is ‘Super female'.

Note: Each cell of Drosophila decides whether to be male or female independently of the rest of the organism, resulting in the occasional occurrence of gynandromorphs i.e. Organism that contains both male and female characteristics. Drosophila was among the first organisms used for genetic analysis. Thomas Hunt Morgan began using fruit flies in experimental studies of heredity at Columbia University in 1910 in a laboratory known as the Fly Room.