2025 Fundamental Animal Microgenetics Complete Practice Exam

A normal female duck possesses a ZW chromosome pairing, distinguishing it from the typical XX pairing found in most mammals. In birds, including ducks, the sex determination system is somewhat reversed compared to mammals. Here, females are designated as ZW and males as ZZ.

The Z chromosome is considered the 'female' chromosome, while the W chromosome is the 'male' chromosome in this chromosomal system. Therefore, when determining the sex of birds, the presence of the W chromosome signifies a female, making the ZW pairing characteristic of female ducks.

This system of sex determination is a classic example of how various species have evolved different methods to define sex based on their genetic make-up, underlining the diversity found in the animal kingdom. The other options provided, such as XX and XY, apply to mammals, while YY does not represent any typical sexual pairing in ducks or other birds. Thus, ZW is the correct and accurate representation of a normal female duck's chromosomal configuration.