Genetics of shell ground colour in Helix aspersa I. Colour locus, uniform and their interactions

Abstract

In Helix aspersa the shell may present basically three colours, yellow, red and brown, each due to an allele of locus C. Heterozygotes as a rule are of intermediate colour, but in some lines one allele may more or less dominate. Colour is better scored in young, adults acquiring a brownish tinge due to periostracum tanning. Another colour locus, not linked with C, is U, dominant, for uniformly distributed reddish dark brown colour epistatic over the effects of all C alleles. U also suppresses all types of band, the manifestation of darker upper part of the shell and the development of fascia albata, producing a shell surface devoid of structural markings. Effect of U on bands is distinct from that due to allele M0 of the locus for intensity of band pigmentation, which does not affect shell structure and colour. Separation of the several effects of U by crossing-over has not been detected. One observed mutation from the recessive u to U, which at once produced all the effects of U, is in favour of these being truly pleiotropic, not due to closely linked genes. © 1984 The Genetical Society of Great Britain.