Question

Which of the following genotypes represent intersex Drosophila?
A. $2A + XXX$
B. $2A + XXY$
C. $3A + XXY$
D. $2A + XY$

Answer 1

Drosophila is also known as the common fruit fly. In the field of biological research, it is one of the most extensively studied organisms. The first use of these organisms was to study the pattern of inheritance as well as the effects of mutation.

Complete answer:
The total number of chromosomes in a Drosophila is $4$. Out of which three are autosomes and a single-sex chromosome. If the ratio of the X chromosome to the total number of chromosomes is between $0.5$ and $1$, the genotype will be that of Intersex. In the genotype $3A + XXY$, the ratio comes to $0.67$, thus the genotype represents intersex.
Considering the other given options:
$2A + XXX$ also represents an aneuploidy but is not a representation of intersex in the fly. Hence it is not the right option.
$2A + XXY$ is also a representation of aneuploidy, but it also does not represent aneuploidy. Thus it is also not a representation.
$3A + XXY$ is the genotype that represents the males in the species. It is the normal diploid genotype. Hence it is not the right option.
Therefore the most appropriate answer is C, i.e., the $3A + XXY$ genotype represents intersex in Drosophila.

Note: The reasons why Drosophila is used extensively for genetic studies are because: It exhibits sexual dimorphism. It is easy to culture in a simple synthetic culture. It has only a few chromosomes, which is only four.