Often, the visual determination of the sex of birds, especially in young, or not during the breeding season, is difficult due to the absence or weakness of morphological differences in secondary sexual characteristics in males and females. Therefore, owners engaged in breeding birds need to resort to molecular sex determination methods.
The sex of birds is determined by a pair of chromosomes W and Z, while it is important to know that, unlike mammals, including humans, birds are heterogametic in females - they have sex chromosomes of both types - W and Z, whereas in male birds - homogametic, their sex is determined by a pair of Z chromosomes - ZZ,
Molecular genetic sex determination is based on the identification of genes linked to the sex chromosomes of birds.
Interpretation of results:
The result of the study is the genotype for sex chromosomes:
WZ - for females
ZZ - for males
Molecular genetics (for specialists):
In most species of birds, the Z-chromosome is the largest in size, usually 4-5 times, and contains almost all genes linked to sex.
The W chromosome, usually much smaller, is a microchromosome containing a high proportion of repetitive (non-coding) DNA sequences.
Recently, a gene encoding a protein involved in the activation of chromatin transcription was discovered on the W chromosome.
According to modern data, the determination of sex in birds occurs by the balance mechanism, when the ratio of autosomes to the Z chromosome is a determining factor in the formation of sex.
DNA sequences homologous to genes that determine sex in humans have been found in both females and male birds, but it is not clear that they perform similar functions in birds.