A critique of avian CHD-based molecular sexing protocols illustrated by a Z-chromosome polymorphism detected in auklets


  • Present addresses: Department of Biological Sciences, University of Stirling, Stirling, FK9 4LA, UK, *Department of Biology, Memorial University of Newfoundland, St John’s, Newfoundland, A1B 3X9, Canada.

T. Burke. Fax: + 44 (0)114 2220002; E-mail: T.A.Burke@Sheffield.ac.uk


The sexes of non-ratite birds can be determined routinely by PCR amplification of the CHD-Z and CHD-W genes. CHD-based molecular sexing of four species of auklets revealed the presence of a polymorphism in the Z chromosome. No deviation from a 1:1 sex ratio was observed among the chicks, though the analyses were of limited power. Polymorphism in the CHD-Z gene has not been reported previously in any bird, but if undetected it could lead to the incorrect assignment of sex. We discuss the potential difficulties caused by a polymorphism such as that identified in auklets and the merits of alternative CHD-based sexing protocols and primers.