カイコ

The fibroin heavy chain of an inbred strain of Bombyx mori was shown to give a single band on SDS-polyacrylamide gel electrophoresis. From the mobility of the band characteristic to the strain, the fibroin heavy chain was classified into three groups, F, M and S. Linkage experiments of the fibroin heavy chain gene, Fib-H, was performed using various silkworm stocks carrying genetic markers on each chromosome. Inconsistent relationship was obtained after observation of the relevant phenotypes, the Fib-H gene segregated in linked fashion with the Nd on the 25th chromosome and with the Nd-t on the 23rd chromosome. This confusion which prevailed for several years was resolved through another series of experiments, made in parallel with present studies, to analyze genetic nature of the Nd-t. Morphological mutants tub and oy were used as the marker gene for the chromosome 23 and the 25, respectively. The mutant Nd-t was not a gene mutation but a chromosomal aberration that can be designated as T(23;25)Nd. The chromosome on which Fib-H gene is located was determined to be the 25th by observing the fibroin heavy chain phenotype in the pedigree of the cross tub oy Fib-H”/ ++Fib-H^S♀×tub oy Fib-H^M♂.