Molecular Sexing in Owls (Aves, Strigiformes) and the Unique Genetic Structure of the Chromodomain Helicase DNA-Binding Protein 1 (CHD1) Gene on Chromosome W.

BACKGROUND

The accurate determination of bird sex is crucial in various biological fields, including ecology, behavioral research, and conservation. However, this task remains challenging in species in which males and females exhibit similar external morphologies, such as owls. Although polymerase chain reaction (PCR)-based molecular sexing techniques that target the chromodomain helicase DNA-binding protein 1 gene found on sex chromosomes Z ( gene) and W ( gene) are widely used, we encountered atypical banding patterns when applying the previously reported primers 2550F and 2718R to four wild owls of unknown sex. This study aims to reveal the owl-specific genetic structure of the gene.

METHODS

We developed a new primer set and determined the nucleotide sequences-including the binding sites for the primers 2550F and 2718R-within both the and genes.

RESULTS

Sequencing analysis, conducted using a newly developed primer set that successfully amplified both Z- and W-derived products across various owl species, revealed a unique genetic insertion of approximately 600 bp in intron 17 of the gene. This insertion reversed the usual length relationship between PCR products from the chromosomes Z and W. Additionally, mutations identified in the 2550F primer binding site of the gene in certain owl species may explain the failure to amplify -derived PCR products.

CONCLUSION

These findings provide valuable insights for improving molecular sexing in owls.