Sex chromosome associated satellite DNA: Evolution and conservation

Abstract

Satellites visible in female but not in male DNA were isolated from the snakes Elaphe radiata (satellite IV, p = 1.708 g x cm-3) and Bungarus fasciatus (BK1 minor, p = 1.709 g x cm-3). The satellites cross hybridize. Hybridization of 3H labelled nick translated BK minor satellite DNA with the total male and female DNA and/or chromosomes in situ of different species of snakes revealed that its sequences are conserved throughout the snake group and are mainly concentrated on the W chromosomes. Snakes lacking sex chromosomes do possess related sequences but there is no sex difference and visible related satellites are absent. The following conclusions have been reached on the basis of these results. 1. The W chromosome associated satellite DNA is related to similar sequences scattered in the genome. 2. The origin and increment in the number of the W satellite DNA sequence on the W chromosome is assoicated with the heterochromatinization of the W. 3. Satellite sequences have become distributed along the length of the W and resulted in morphological differentiation of sex chromosomes. 4. Evolutionary conservation of W satellite DNA strongly suggests that functional constraints may have limited sequence divergence.

Single locus inheritance and joint segregation analysis of minisatellite (VNTR) DNA loci in brown trout (Salmo trutta L.)

“…Other types of repetitive DNA have also been linked to sex determining locations. For example Bkm satellite DNA, which contains numerous GATA-GACA repeats, is associated with sex determining chromosomes in snakes (Singh et a!., 1980); mice (Jones & Singh, 1982) and sea turtles (Demas et a!., 1990). While Bkm sequences have been shown to detect DNA fingerprint patterns in both rainbow trout (Lloyd et al, 1989) and in the coral reef fish, Anthias squamipinnis (Wachtel & Demas, 1991), no evidence of sex association was found in either study.…”

A ZZ/ZW Sex Chromosome System in Imparfinis mirini (Pisces, Siluriformes).

“…Although knowledge about the mechanisms related to the origin of sex chromosomes in fishes is still poor, several studies have proposed that the evolution of these heteromorphic sex chromosomes depends of the suppression of crossing-over between sex-allele-carrying chromosomes due to chromosome rearrangments and/or to the accumulation of repetitive DNA sequences on one particular chromosome, usually the Y or W (Singh et al 1980, Becak 1983, Galetti and Foresti 1987, Koehler et al 1995. The presence of W chromosomes with large heterochromatin segments in species belonging to groups not directly related suggests that common features possibly resulted in the origin of such elements.…”

Extension, single-locus conversion and physical mapping of sex chromosome sequences identify the Z microchromosome and pseudo-autosomal region in a dragon lizard, Pogona vitticeps

“…A comparative analysis of sex-related sequences and chromosomes is perhaps the most tractable of these approaches, but it requires the initial identification of sex-related sequences. There are very few sex-specific sequences reported for reptiles (Cooper et al, 1997;Halverson and Spelman, 2002), although repetitive satellite sequences are known to be interspersed throughout the chromosomes of snakes in high copy number (Singh et al, 1976(Singh et al, , 1980 and are concentrated in particularly high density on the W chromosome (Solari, 1994). A number of functional genes have recently been mapped to the Z and W chromosomes of three snakes, a gecko and a turtle (Matsubara et al, 2006;Kawaia et al, 2007;Kawagoshi et al, 2009).…”