A DNA test to sex most birds

Mol Ecol. 1998 Aug;7(8):1071-5. doi: 10.1046/j.1365-294x.1998.00389.x.


Birds are difficult to sex. Nestlings rarely show sex-linked morphology and we estimate that adult females appear identical to males in over 50% of the world's bird species. This problem can hinder both evolutionary studies and human-assisted breeding of birds. DNA-based sex identification provides a solution. We describe a test based on two conserved CHD (chromo-helicase-DNA-binding) genes that are located on the avian sex chromosomes of all birds, with the possible exception of the ratites (ostriches, etc.; Struthioniformes). The CHD-W gene is located on the W chromosome; therefore it is unique to females. The other gene, CHD-Z, is found on the Z chromosome and therefore occurs in both sexes (female, ZW; male, ZZ). The test employs PCR with a single set of primers. It amplifies homologous sections of both genes and incorporates introns whose lengths usually differ. When examined on a gel there is a single CHD-Z band in males but females have a second, distinctive CHD-W band.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Avian Proteins*
  • Base Sequence
  • Birds / genetics*
  • Chickens / genetics
  • DNA / analysis*
  • DNA / chemistry
  • DNA Primers / chemistry
  • DNA-Binding Proteins / genetics*
  • Electrophoresis, Agar Gel / veterinary
  • Electrophoresis, Polyacrylamide Gel / veterinary
  • Female
  • Introns / genetics
  • Male
  • Mice
  • Molecular Sequence Data
  • Polymerase Chain Reaction / veterinary
  • Sequence Alignment
  • Sequence Analysis, DNA / veterinary
  • Sequence Homology, Nucleic Acid
  • Sex Chromosomes / chemistry
  • Sex Chromosomes / genetics*
  • Sex Determination Analysis / veterinary*


  • Avian Proteins
  • CHD-W protein, Gallus gallus
  • CHD-Z protein, Gallus gallus
  • Chd1 protein, mouse
  • DNA Primers
  • DNA-Binding Proteins
  • DNA

Associated data

  • GENBANK/AF006659
  • GENBANK/AF006660
  • GENBANK/AF006661
  • GENBANK/AF006662