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Which one of the following conditions correctly describes the manner of determining the sex?
Homozygous sex chromosomes $(ZZ)$ determine female sex in birds
$XO$ type of sex chromosomes determine male sex in grasshopper
$XO$ condition in humans as found in Turner's syndrome determines female sex
Homozygous sex chromosomes $(XX)$ produce males in Drosophila
Solution
$XO$ type of sex chromosomes determine male sex in grasshoppers. This type of sex-determination comes under $XX – XO$ type. It is common in cockroaches, grasshoppers and bugs. The female has two homomorphic sex chromosomes $X X$ and is homogametic. It produces similar eggs, each with one $X-$ chromosome. The male has one chromosome only and is heterogametic. It produces two types of sperms-gynosperms with $X$ and androsperms without $X$.
Other statements can be corrected as follows
In birds, the females are heterozygous and represented as $ZW.$
Female sex in humans is represented as $XX.$
In Drosophila, males are heterogametic, i.e, $XY.$
