Isolation and characterization of BKM satellite DNA from snake Bungarus Fasciatus and a BKM associated Y Chromosome-Specific clone M34 from mouse

Abstract

Cytogenetic and molecular studies on the sex chromosomes of snakes newlinehave unequivocally revealed that the W chromosome is enriched with newlineinterspersed repetitive DNA. Such repetitive DNA can be isolated as a newlinesatellite fraction from the female genomic DNA by isopycnic density newlinegradient centrifugation. Such a satellite fraction isolated from female newlinebanded krait genomic DNA has been designated as banded krait minor newline(Bkm) satellite DNA. Bkm sequences have been reported to be newlineconserved in a wide range of eukaryotes. In situ hybridization using newlineBkm probe on metaphase chromosome preparations of species with newlinemorphologically distinguishable sex chromosomes has confirmed that newlineBkm is predominantly localized on the W chromosome in snakes and newlineon the Y chromosome in mouse. Sequencing of positive clones, newlinerecovered by screening mouse and Drosophila genomic libraries with newlineuncloned Bkm has revealed the presence of a consensus sequence of a newlinetetranucleotide repeat GATA. This repeat isolated from Drosophila newlinegenomic library is designated as Bkm 2(8). However, all Bkm positive newlineclones of Drosophila do not show hybridization with Bkm 2(8) newlineindicating the presenc_e of a second component in the Bkm which is newlineconserved between Drosophila and snake. Screening of mouse and newlinehuman genomic libraries with Bkm 2(8) has resulted in the isolation of newlinespecies and sex-specific clones-M34 and pi 02d(2) respectively, newlinesuggesting the possible occurrence of such sex and species-specific newlinesequences in snakes also, which may be co-purified with Bkm. newlineviii newlineA striking similarity in the molecular organizati9n of the W newlinechromosome in snake and Y chromosome in mouse has been newlinedemonstrated using Bkm and M34 probes. In situ hybridization has newlinerevealed that Bkm and M34 sequences are localized throughout the newlinelength of the W and the Y chromosomes respectively, except in the sex newlinedetermining region of mouse. To further our understanding of the newlinemolecular organization of sex chromosomes, the following newlineinvestigations have been undertaken in the present study .