Question

Assume that you are told that a particular organism, Drosophila, has the XO chromosome

complement. You are also told that the autosomal complement is a normal 2n. You know that in
humans the XO complement is female determining. Would you be correct in assuming that the
Drosophila sex for XO is also female? Choose the answer that includes the correct explanation.
A) No, the chromosomal basis for sex determination in Drosophila is based on the balance
between the number of X chromosomes and haploid sets of autosomes.
B) Yes, because sex determination in humans and insects is essentially the same.
C) No, it takes two X chromosomes to produce a female in humans and a Y chromosome to
produce a male in Drosophila.
D) Yes, the presence of an X chromosome determines a female in both organisms.
E) No, sex determination in Drosophila is dependent on the presence or absence of the Y
chromosome.

Answer 1

In Drosophila sex determination, an XO chromosome complement results in a male, not a female as in humans, because it relies on the ratio of X chromosomes to autosomes.

Step-by-step explanation:

The correct answer to the question of whether an organism with an XO chromosome complement in Drosophila is female is A) No, the chromosomal basis for sex determination in Drosophila is based on the balance between the number of X chromosomes and haploid sets of autosomes. Unlike in humans, where the presence of XX chromosomes usually indicates a female and XY indicates a male, Drosophila follows a different system. In Drosophila, males typically have an XY chromosome pair, while females are XX.

An XO complement in Drosophila leads to a male because the sex determination is based on the ratio of the number of X chromosomes to autosomes, not simply the presence or absence of the Y chromosome as in humans. In humans and many other animals, an XO chromosome complement might be associated with Turner syndrome, which is characterized by females with a single X chromosome.