An X-autosome fusion chromosome of Caenorhabditis elegans.
The translocation mnT12(IV;X) is a fusion of holocentric chromosomes IV and X, the breakpoints occurring near the left end of IV and the right end of X. Animals homozygous for mnT12 are viable and fertile; they contain five pairs of chromosomes rather than the normal set of six pairs. The mnT12 chromosome is larger than all wild-type chromosomes and thus identifies linkage groups IV and X cytologically. Hermaphrodites heterozygous for mnT12 show high frequency meiotic nondisjunction both between mnT12 and the X chromosome, which results in a high incidence of male self progeny (27% compared to the wild-type incidence of 0.2%), and between mnT12 and chromosome IV, which results in a high incidence of self progeny essentially trisomic for chromosome IV (karyotype IV/mnT12/mnT12). The viability of chromosome IV trisomics has been confirmed by constructing animals trisomic for only normal copies of chromosome IV; these animals are morphologically wild type. Meiotic chromosome disjunction in mnT12 homozygotes appears to be normal, although the frequency of recombination between markers that are normally X-linked is significantly reduced. Males of genotype IV/mnT12/0 are fertile. They can be thought of as having a neo-X(mnT12) neo-Y(normal IV) karyotype since it is possible to maintain a male-hermaphrodite stock of C. elegans consisting of such males and hermaphrodites carrying two neo-X chromosomes and no neo-Y; the organism is thus converted from an XO:XX type of sex determination to an XY:XX system.
Sigurdson
D C
DC
Herman
R K
RK
Horton
C A
CA
Kari
C K
CK
Pratt
S E
SE
D000818:Animals; D002107:Caenorhabditis / Q000235:genetics*; D002874:Chromosome Mapping; D002875:Chromosomes / Q000502:physiology*; D008040:Genetic Linkage; D005838:Genotype; D006720:Homozygote; D014178:Translocation, Genetic; D014960:X Chromosome / Q000502:physiology*