Mammalian genomes can vary substantially in haploid chromosome number even within a small taxon (e.g., 3-40 among deer alone); in contrast, teleost fish genomes are stable (24-25 in 58% of teleosts), but we do not yet understand the mechanisms that account for differences in karyotype stability. Among perciform teleosts, platyfish (Xiphophorus maculatus) and medaka (Oryzias latipes) both have 2...

In previous papers in this series (5, 8, I3) it has been shown that spontaneous malignant melanomas are produced in the hybrid offspring of the black-spotted platyfish, Platypoecilus maculatus, and the swordtail, Xiphophorus hdlerii. The melanomas are evoked genetically in hybrids by the interaction of the sexlinked, heritable factor for macromelanophores, Sp, of the platyfish with a series of ...

In contrast to the situation observed in mammals and birds, a switching between different sex determination systems frequently occurred during the evolution of the teleost fish lineage. This might be due to a frequent turnover of sex-determining signals at the top of the sex determination cascade (master sex-determining genes in the case of genetic sex determination). Alternatively, different v...

Color pattern polymorphisms are widespread in animals, and are found within populations, among populations, and among species. The southern platyfish, Xiphophorus maculatus, represents one of the most extreme examples of color pattern polymorphism. Extensive research with this model system for melanoma formation has resulted in an understanding of the underlying genetic basis of over 40 sex-lin...

The present study focused on conducting in silico analysis and investigating the tissue-specific distribution expression of catalase gene platyfish (Xiphophorus maculatus), which can be used as a model organism for studying stress responses fish. Assay steady-state levels cat transcripts by real time PCR revealed. level transcript was abundant liver (2162.21) compared with intestine (1270.94), ...

ent sword as a control. Because swordlessness is the ancestral state of the Xiphophorus clade, Basolo argues that the results of her experiment indicate that female preference for swords predates the evolution of the sword and concludes that coevolutionary models of sexual selection are inadequate. Basolo provides no direct evidence in support of a preexisting female sensory bias, but rejects t...

The genetic basis of spontaneous melanoma formation in spotted dorsal (Sd) Xiphophorus platyfish-swordtail hybrids has been studied for decades, and is adequately explained by a two-gene inheritance model involving a sex-linked oncogene, Xmrk, and an autosomal tumor suppressor, DIFF. The Xmrk oncogene encodes a receptor tyrosine kinase related to EGFR; the nature of the DIFF tumor suppressor ge...

In natural populations of platyfish, Xiphophorus maculatus, there are three sex chromosomes--W, X, and Y. Females may have one of three genotypes: WY, WX, or XX, and males may have either XY or YY. The W chromosome can be considered a modified X that blocks the male-determining function of the Y. The platyfish may represent an evolutionary stage at which female heterogamety arises through a sin...

When a black-spotted female platyfish (Platypoecilus maculatus) is mated to an unspotted (genetically recessive) male platyfish, one of three hereditary expressions may be expected. If the female is genetically pure (homozygous dominant) for the spotted factor, all of the young may be expected to be spotted. The genetic formula representing this situation is (W)Sp(Z)Sp, for the mother, where W ...