Alleles at the white Locus

There can be many different alleles of a single gene. In fact, the actual number is infinite, as any particular base pair can be changed to any other, and any possible new DNA sequence can be inserted, and any amount can be deleted. Some alleles will produce gene products with no function, others may produce products with partial function. Even if several different mutant alleles are recessive to wild type, they may still be dominant to other alleles. Usually, alleles that fully inactivate a gene are recessive in all heterozygous combinations, and alleles with only a slight loss of function are dominant to alleles with a more severe loss of function. To see just how complicated this can all become, here is a partial list of mutant alleles at the white locus of Drosophila melanogaster, taken from "Genetic Variations of Drosophila melanogaster" by D. L. Lindsley and E. H. Grell, Carnegie Institution of Washington Publication No. 627, 1968. In 1968, there were 154 different alleles listed in the book; there were probably thousands that had been found but were not listed; more have been found since then.

w: white origin: spontaneous discoverer: Morgan references: Morgan, Science 32: 120 (1910) phenotype: eyes pure white	w^bf: white-buff origin: spontaneous discoverer: Safir references: Genetics 1: 584 (1916) phenotype: eyes light buff, lighter than w^e male. w^bf male eyes somewhat lighter than female.
w^+A: American wild-type allele of white discoverer: Timoféef-Ressovsky references: Timoféef-Ressovsky, Biol. Zentr. 52: 468 (1932) phenotype: eyes pinkish at eclosion, darken to maroon, but never become a normal red.	w^bl: white-blood origin: spontaneous discoverer: Hyde references: Genetics 1: 535 (1916) phenotype: eyes yellowish ruby at hatching, darkening to sepialike with age; female lighter than male.
w^+O: Oregon-R wild-type allele of white origin: in Oregon-R wild type strain discoverer: Green references: Green, Proc. Natl. Acad. Sci. U. S. 45: 549 (1959) phenotype: amount of pigment in diploid w^+O/w less than w^+C/ w but difference is not readily detected visually.	w^Bwx: white-Brownex origin: spontaneous discoverer: Mossige references: Dros. Info. Serv. 27: 59 (1953) phenotype: eye color like bw ; no sexual dimorphism
w^+C: Canton-S wild-type allele of white origin: In Canton-S wild type strain discoverer: Green references: Green, Proc. Natl. Acad. Sci. U. S. 45: 549 (1959) phenotype: (see description of w^+O)	w^cf: white-coffee origin: Xray induced discoverer: Nicoletti references: Nicoletti, Dros. Info. Serv. 34: 52 (1960) phenotype: eyes deep ruby at hatching, but darken greatly with age.
w^a: white-apricot origin: spontaneous discoverer: Huestis, 1923 references: Morgan, Bridges, and Sturtevant, Bibliog. Genet. 2: 218 (1925) phenotype: eyes of male yellowish with orange tone; female eyes yellower, somewhat lighter than male.	w^ch: white-cherry origin: spontaneous discoverer: Safir references: Biol. Bull. 25: 45 (1913) phenotype: eyes translucent pink, only slightly yellowish.
w^a2 origin: spontaneous discoverer: Bridges, 1929 references: Dros. Info. Serv. 9: 114 (1938) phenotype: eye color orange, slightly darker than w^a. Eyes of male darker than female.	w^e: white-eosin origin: spontaneous derivative of w discoverer: Morgan references: Morgan and Bridges, Carnegie Inst. Wash. Publ. No. 237: 28 (1916) phenotype: eyes of female yellowish pink, male and w^e/ w lighter.
w^a3 origin: spontaneous discoverer: Curry references: Dros. Info. Serv. 9: 114 (1938) phenotype: eyes brownish orange; slightly darker than either w^a or w^a2. Very little sex difference	w^m4: white-mottled 4 origin: Xray induced discoverer: Muller, 1929 references: J. Genet. 22: 299 (1930) phenotype: eyes variegated