In this review, we focus on the evolution of sex chromosome-autosome fusions, which appear to be quite common in fishes. This suggests that the male-determining region on the Y chromosome should be relatively small. Murofushi et al. Conclusions Species with multiple sex chromosome systems are prevalent in fishes.
Extensive genomic analyses have been conducted on the Drosophila miranda neo-sex chromosome created by a Y-autosome fusion; these studies have provided insights into the evolutionary forces that drive the degeneration of the Y chromosome Bachtrog and Charlesworth ; Bachtrog ; Bachtrog ; Bachtrog ; Bachtrog et al.
We have tested this idea by performing genetic linkage analysis of the isolating barriers present between the Japan Sea form X 1 X 2 Y and the Pacific Ocean form XY of threespine sticklebacks. Only three of these were expressed in embryos; and only one gene, called DMYwas expressed exclusively in XY embryos and was present on the Y but not on the X chromosome.
However, genes that play a role in reproductive isolation between populations might accumulate on neo-sex chromosomes for many of the same reasons that they are found on ancestral sex chromosomes. The behavioural ecology of sticklebacks.
Cytotaxonomic studies in Cyprinodontidae: multiple sex chromosomes in Garmanella pulchra. Karyotypic survey, geographic distribution of cytotypes and cytotaxonomic considerations.
Recently, we found that a population of threespine stickleback Gasterosteus aculeatus from Japan has an X 1 X 2 Y multiple sex chromosome system resulting from a fusion between the ancestral Y chromosome and an autosome, while a sympatric threespine stickleback population has a simple XY sex chromosome system.
Sequencing of about kb from this region led to the identification of 52 putative genes. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author s and source are credited.
For example, a new female-determination locus has evolved chromosomal sex determination in melandrium and fishes of hawaii in Roseville species of Lake Malawi cichlids, and a gene involved in sexually dimorphic pigmentation is tightly linked to the female sex-determination locus on the invading W chromosome Roberts et al.
Summary An excellent candidate for the master sex-determining gene on the Y chromosome of the medaka fish is not related to the mammalian SRY gene. However, we have not yet confirmed that spine length is a sexually antagonistic trait or identified any genes with sexually antagonistic alleles on the ancestral autosome chromosome 9 of the Pacific Ocean population.
In this review, we focus on the evolution of sex chromosome-autosome fusions, which appear to be quite common in fishes.
Ueno and Takai Animal Cytology and Evolution. Fusions between an autosome and a sex chromosome X, Y, Z, or W create what is commonly referred to as a multiple sex chromosome system. In this review, we focus on the evolution of sex chromosome-autosome fusions, which appear to be quite common in fishes.
Uyeno and Miller The presence of multiple sex chromosome systems in diverse groups of fishes suggests that they have evolved independently in multiple lineages.