Genetic analysis of a new mutation 'extra-abdominal legs and extra crescents' belonging to the E pseudoalleles in the silkworm, Bombyx mori.

摘要

New mutant larvae were discovered in a hybrid race, C21 x Koishimaru, of the silkworm, Bombyx mori. Genetic analysis indicated that the mutant character was controlled by a single dominant gene belonging to the E pseudoalleles, located at position 21.1 on the 6th-linkage group. This new mutant was named 'Extra-abdominal legs and extra crescents', with the gene symbol EAl. The phenotype of the EAl mutant was as follows. EAl heterozygous larvae showed two pairs of extra-abdominal legs on the first- and second-abdominal segments and a pair of extra-crescent markings on the first-abdominal segment. The majority of EAl homozygous larvae developed to the adult stage. The EAl homozygous larvae showed nearly the same characters as EAl heterozygotes, but expression of the extra-abdominal legs and extra-crescent markings was slightly clearer than those in the heterozygous larvae. Although copulatory behaviour and fertility were normal in EAl heterozygous moths, EAl homozygous moths were predominantly sterile in both sexes. Recombination between EAl and EDn was not recognized, but those between EAl and ENc were detected, of which the value was 0.08%. The strain carrying the recombinant chromosome (EAl ENc/+ +) was established and maintained..