VIII.—A Case of Non-disjunction in the Fowl

Abstract

The application of the facts of criss-cross inheritance to commercial poultry breeding is widespread, and every year witnesses the hatching of thousands of chickens, the plumage-colour character of whose mothers was genetically silver, whilst that of their sires was genetically gold. Dominant silver and its allelomorph, recessive gold, form a pair of sexlinked characters, the genes corresponding to them being placed in the X-chromosome. Such evidence as exists points directly to the conclusion that in the fowl the male is the homogametic sex (XX), the female the heterogametic (XY or XO). The mating silver hen, (SX)Y, and gold cock, (sX) (sX), gives, in more or less equal numbers, gold daughters, (sX)Y, and silver sons, (SX) (sX), and, since these colours can readily be distinguished in the newly hatched chick, it is possible to identify males and females amongst day-olds by reference to their down colour. The diagnostic value of a sex-linked character depends upon the precision of the distributive mechanism of the sex-chromosomes.

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

“…In the absence of a clear consensus about the role of Z and W chromosomes in sex determination of birds, it seems pertinent to add the observations of Durham (1926) to the widely quoted case of Crew (1933) which, in the judgement of some workers and as re-examined here, disproves H D . In canaries, H B is acceptable unequivocally (P = 087) while the strength of rejection of// D depends largely on assumed disjunction rates in female meiosis.…”

“…Crew's (1933) data pertain to one of several exceptional, patroclinous gold roosters produced by a Rhode Island Red male (ss, gold) with Light Sussex females (S, silver). As may be seen in Table 1, his karyotype was either ZO (by // D ) or ZZW (by H B ) as stated by Crew and accepted by Abbott & Yee (1975) but not by Hutt (1949: 474).…”

“…(3) Crew's (1933) often quoted ZZW rooster. In addition, / / B is supported by 'half-sider' gynandromorphs (Hutt, 1949: 471;Taber, 1964) where left and right sides of the bird differ not only in Z-linked plumage traits, implying sex chromosome mosaicism (ZZZ/ZO from mitotic nondisjunetion or ZZ/ZO from chromatid loss), but also in sex of gonad implying development of functional structures of both sexes in the absence of a W chromosome.…”

“…Duncker, 1928;Crew, 1933) questioned the Drosophila scheme of sex determination in birds, as that was universally accepted for birds and mammals until the male-determining role of the mammalian Y was discovered (Stern, 1973: 503). This report re-examines the data of Crew (1933) and analyses for the first time part of the data of Durham (1926). Both sources support the 'balance scheme' of sex determination (H B ) m birds.…”

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

“…Unfortunately, karyotype analysis has so far failed to reliably identify individuals with the truly informative genotypes such as ZO and ZZW. While a single report of a male ZZW aneuploid would appear to support the Z chromosome:autosome ratio model [44], others have convincingly argued that cytological techniques available at that time were not sufficiently reliable to assign a credible karyotype [45]. The most detailed karyotyping studies available in birds have resulted from the analysis of a triploid line of identify a direct homologue to the mammalian testis-determining gene (Sry) have so far proved unsuccessful, although a large number of related SOX (Sry box) genes have been identified [58][59][60].…”