Sex determination in birds: progeny of nondisjunction canaries of Durham (1926)

Abstract

The heterogametic sex in birds (ZW) is female for presence of the W or for lack of a second Z chromosome. These alternatives can be distinguished given ZO or ZZW aneuploids and segregation of a .Z-linked marker in their progeny. Having discovered the Z-linked cinnamon locus with two alleles (B, black eyes; b, red eyes), Durham observed 21 black-eyed daughters (BO or BbW) of bb cocks and B hens. Using Durham's data on sex-colour phenotypes of 14 young of two of the 21 matroclinous females show that the sex chromosome constitution of the two exceptional hens were more likely ZO than ZZW. This case plus that of Crew's (1983) trisomic rooster (ZZW) shows that sex determination in birds follows the 'genie balance' scheme as in Drosophila, not the ' dominant Y' scheme as in mammals.

An overview of factors influencing sex determination and gonadal development in birds

“…These are based on models established in other organisms with heteromorphic sex chromosomes and propose that the sex-determining mechanism in birds is regulated by either a dominant genetic switch as employed by mammals or a dosage-based mechanism as typified by the systems in operation in Drosophila and Caenorhabditis elegans [6, 15,35,36]. In mammals, the male-specific gene Sry, located on the Y chromosome, has been identified as the testis-determining gene [37,38].…”

Proposed role of W chromosome inactivadon and the absence of dosage compensation in avian sex determination

“…based on a dominant W chromosome) (Abdel-Hameed & Shoffner 1971;McCarrey & Abbott 1979). Sittmann (1984) analysed the inheritance of a Zlinked marker in data collected by Durham (1926) on the progeny of two matroclinous female canaries, and favoured the view that the two females were more likely to be ZO than ZZW. These data, and those on an abnormal rooster which Crew (1933) thought was ZZW, led Sittmann to suggest that sex determination in birds may be similar to that in Drosophila.…”