title: Partial deletions of the W chromosome due to reciprocal translocation in the silkworm Bombyx mori.
abstract: In the silkworm, Bombyx mori (female, ZW; male, ZZ), femaleness is determined by the presence of a single W chromosome, irrespective of the number of autosomes or Z chromosomes. The W chromosome is devoid of functional genes, except the putative female-determining gene (Fem). However, there are strains in which chromosomal fragments containing autosomal markers have been translocated on to W. In this study, we analysed the W chromosomal regions of the Zebra-W strain (T(W;3)Ze chromosome) and the Black-egg-W strain (T(W;10)+(w-2) chromosome) at the molecular level. Initially, we undertook a project to identify W-specific RAPD markers, in addition to the three already established W-specific RAPD markers (W-Kabuki, W-Samurai and W-Kamikaze). Following the screening of 3648 arbitrary 10-mer primers, we obtained nine W-specific RAPD marker sequences (W-Bonsai, W-Mikan, W-Musashi, W-Rikishi, W-Sakura, W-Sasuke, W-Yukemuri-L, W-Yukemuri-S and BMC1-Kabuki), almost all of which contained the border regions of retrotransposons, namely portions of nested retrotransposons. We confirmed the presence of eleven out of twelve W-specific RAPD markers in the normal W chromosomes of twenty-five silkworm strains maintained in Japan. These results indicate that the W chromosomes of the strains in Japan are almost identical in type. The Zebra-W strain (T(W;3)Ze chromosome) lacked the W-Samurai and W-Mikan RAPD markers and the Black-egg-W strain (T(W;10)+(w-2) chromosome) lacked the W-Mikan RAPD marker. These results strongly indicate that the regions containing the W-Samurai and W-Mikan RAPD markers or the W-Mikan RAPD marker were deleted in the T(W;3)Ze and T(W;10)+(w-2) chromosomes, respectively, due to reciprocal translocation between the W chromosome and the autosome. This deletion apparently does not affect the expression of Fem; therefore, this deleted region of the W chromosome does not contain the putative Fem gene.
authors: Department of Biological Production, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Japan. wfem@cc.tuat.ac.jp
authors: H
authors: H
authors: Abe
authors: M
authors: M
authors: Seki
authors: F
authors: F
authors: Ohbayashi
authors: N
authors: N
authors: Tanaka
authors: J
authors: J
authors: Yamashita
authors: T
authors: T
authors: Fujii
authors: T
authors: T
authors: Yokoyama
authors: M
authors: M
authors: Takahashi
authors: Y
authors: Y
authors: Banno
authors: K
authors: K
authors: Sahara
authors: A
authors: A
authors: Yoshido
authors: J
authors: J
authors: Ihara
authors: Y
authors: Y
authors: Yasukochi
authors: K
authors: K
authors: Mita
authors: M
authors: M
authors: Ajimura
authors: M G
authors: MG
authors: Suzuki
authors: T
authors: T
authors: Oshiki
authors: T
authors: T
authors: Shimada
mesh_terms: D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D002872:Chromosome Deletion; D022202:Chromosomes, Artificial, Bacterial; D004247:DNA / Q000737:chemistry / Q000235:genetics; D005260:Female; D015723:Gene Library; D005819:Genetic Markers; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008969:Molecular Sequence Data; D019105:Random Amplified Polymorphic DNA Technique; D018626:Retroelements / Q000235:genetics; D012729:Sex Chromosome Aberrations; D012730:Sex Chromosomes / Q000235:genetics*; D014178:Translocation, Genetic / Q000235:genetics*
chemical_list: D005819:Genetic Markers; D018626:Retroelements; D004247:DNA