​The following represents a Southern hybridization of restricted genomic DNA, probed with a DNA fragment corresponding to gene ‘Z’.

Gene ‘Z’ is a single copy gene.

The hybridization patterns of parents and their progeny have been presented in the image.

Which one of the following options is a correct interpretation of the observation?

Correct option is C

​Explanation:

(A) Gene ‘Z’ is present on an autosome.

• If this were true, both males and females would inherit it equally.
• The observed inheritance pattern suggests a sex-linked gene, so this is incorrect.

(B) Gene ‘Z’ is an example of an X-linked gene.

• If this were true, the pattern would be seen in an XY sex determination system, where males inherit the gene from their mother.
• However, if the organism follows a ZW system, this statement is incorrect.

(C) In this organism, the female is the heterogametic sex.

• The hybridization pattern suggests that the gene follows Z-linked inheritance.
• The banding pattern in the hybridization result suggests that the male parent has two identical bands while the female parent has only one band or different bands.
• The progeny males inherit the two identical bands (ZZ), and the progeny females inherit different bands (ZW), consistent with a Z-linked gene in a ZW system.
• Females (ZW) inherit different bands, while males (ZZ) inherit the same bands.
• This pattern is typical in birds, reptiles, and some fish, where females are ZW and males are ZZ.

(D) Polymorphism of this gene has been studied by RAPD.

• RAPD is a PCR-based technique for genetic polymorphism detection, but the experiment uses Southern hybridization, which is a different method.