Open AccessCytogenetic Analysis Shows that the Unusually Large Chromosome in the Sex‐Limited p B Silkworm ( Bombyx Mori ) Strain Consists of three Chromosomes
Author(s) -
Yokoyama Takeshi,
Abe Hiroaki,
Tsuchida Kozo,
Ninagi Osamu,
Oshiki Toshikazu
Publication year - 2000
Publication title -
hereditas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 50
eISSN - 1601-5223
pISSN - 0018-0661
DOI - 10.1111/j.1601-5223.2000.t01-1-00095.x
Subject(s) - biology , chromosome , genetics , chromosome 22 , w chromosome , bombyx mori , chromosome 12 , chromosome 18 , chromosome 16 , sex linkage , chromosome 17 (human) , chromosome 7 (human) , chromosome 19 , chromosome 3 , chromosome 4 , microbiology and biotechnology , constitutive heterochromatin , heterochromatin , karyotype , gene
We have discovered an inordinately large chromosome pair at the pachytene stage in the oocyte of the sex‐limited p B (black larval marking) silkworm ( Bombyx mori ) strain (TWPB). We have analyzed the composition and arrangement of this large chromosome. A genetic linkage analysis shows that the large chromosome is made up of the W chromosome, the second chromosome fragment ( p B fragment), and the fifth chromosome (linkage group) containing at least the region from map position 0.0 to 40.8. We also observed a sex heterochromatin body (SB) that we deduced to be made up of condensed W chromosomes. The number of SBs in each female nucleus among the sucking stomach cells of the TWPB strain was variable. Evidently, the W chromosome of the TWPB strain is attached to another chromosome. The composition of the W chromosome, the second chromosome fragment, and the fifth chromosome was studied through linkage analysis for these three chromosomes. We used two strains derived from the TWPB strain, the sex‐limited p M (moricaud larval marking)‐like (TWPML) and the autosomal p M ‐like (T5PML). The results show that the TWPML strain originates through a detachment of the fifth chromosome from the large chromosome of the TWPB strain, and the T5PML strain originates through a detachment of the W chromosome from that. Accordingly, the large chromosome of the TWPB strain is arranged in the order W chromosome—second chromosome fragment—fifth chromosome.