Sex-linkage of the black caudal-peduncle and red tail genes in the tuxedo strain of the guppy, Poecilia reticulata

Two color patterns of the Tuxedo guppy strain commercially cultured in Sing apore were subjected to genetic analyses. Gene control of the black caudal- peduncle and red tail color patterns was elucidated by reciprocal crosses b etween the Tuxedo (TUX) strain and wild-type (WT) stock. F-1 progenies were produced by single-pair crossing between TUX and WT, while the F-2 generat ion was obtained from full-sib mating between F-1 males and females. F-1 an d F-2 data were segregated according to phenotypes and sex, and tested by c hi-square analyses. Both color patterns show single gene inheritance, and a re dominantly expressed in both sexes, sex-linked and determined by differe nt loci on the X- and Y-chromosomes. Alleles for the black caudal-peduncle (Bcp) and red tail (Rdt) loci, are dominant over that of the wild-type, Bcp (+) and Rdt(+), which do not display these color patterns. The typical geno types for TUX guppies are proposed to be XBcp,RdtYBcp,Rdt for males and XBc p,RdtXBco,Rdt for females. Heterozygous TUX males have the XBcp,RdtYBcp,Rdt +, XBcp,RdtYBcp,Rdt+ and XBcp,RdtYBcp,Rdt+ genotypes while the females are XBcp,RdtXBcp,Rdt+. The segregation and inheritance of the Bcp and Rdt genes are illustrated by genetic models. Map distances estimated from F-1 and F- 2 recombinants are approximately 3.4, 5.1 and 2.4 map units for the sex-det ermining region (SdR)-Rdt, SdR-Bcp and Rdt-Bcp, respectively. The gene map order is hypothesized to be SdR-Rdt-Bcp.