title: Extreme nearly neutral evolution in mitochondrial genomes of laboratory mouse strains.
abstract: Relaxation of the selective constraint during the domestication process is known. In this study, we report unexpected closeness to neutral evolution of mitochondrial genomes of laboratory mouse strains: estimated non-synonymous/synonymous rate ratio being very close to 1 (ω^=1.32). Probably it is due to the extreme inbreeding extending over 100 years as well as to their recent origin (middle of the last millennium). There is no rate difference observed among three codon positions as well as ribosomal RNA and control regions. However, the amino acid substitutions occurred not randomly, and substitutions were more frequent between physico-chemically similar amino acids than between dissimilar ones. Probably this is inevitable consequence caused by the codon table itself, but not by selections. This implies that a large portion of the new mutations are conservative, and most of them are slightly deleterious and not lethal. It seems that, even though the selection pressures do not hold normally, the function of genes may not be impaired in most cases.
authors: School of Life Sciences, Fudan Univeristy, HanDan Rd. 220, Shanghai, 200433, China; Institute of the Statistical Mathematics, Midori-cho 10-3, Tachikawa, Tokyo, 190-8562, Japan. Electronic address: cyclotis@gmail.com.
authors: Takahiro
authors: T
authors: Yonezawa
authors: School of Life Sciences, Fudan Univeristy, HanDan Rd. 220, Shanghai, 200433, China; Institute of the Statistical Mathematics, Midori-cho 10-3, Tachikawa, Tokyo, 190-8562, Japan.
authors: Masami
authors: M
authors: Hasegawa
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D003062:Codon; D019143:Evolution, Molecular; D054629:Genome, Mitochondrial; D051379:Mice; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics; D012641:Selection, Genetic
chemical_list: D003062:Codon; D012335:RNA, Ribosomal
keywords: Branch model; CLS; Ka; ML; Ma; Mus musculus domesticus; Slightly deleterious mutation; common laboratory strain; kilo annum; maximum likelihood; mega annum