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

Abstract

Two color patterns of the Tuxedo guppy strain commercially cultured in Singapore were subjected to genetic analyses. Gene control of the black caudal-peduncle and red tail color patterns was elucidated by reciprocal crosses between the Tuxedo (TUX) strain and wild-type (WT) stock. F1 progenies were produced by single-pair crossing between TUX and WT, while the F2 generation was obtained from full-sib mating between F1 males and females. F1 and F2 data were segregated according to phenotypes and sex, and tested by chi-square analyses. Both color patterns show single gene inheritance, and are dominantly expressed in both sexes, sex-linked and determined by different 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 genotypes for TUX guppies are proposed to be XBcp,RdtYBcp,Rdt for males and XBcp,RdtXBcp,Rdt for females. Heterozygous TUX males have the XBcp,RdtYBcp +,Rdt, XBcp,RdtYBcp + ,Rdt + and XBcp,RdtYBcpRdt + 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 F1 and F2 recombinants are approximately 3.4, 5.1 and 2.4 map units for the sex-determining region (SdR)-Rdt, SdR-Bcp and Rdt-Bcp, respectively. The gene map order is hypothesized to be SdR-Rdt-Bcp.