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[摘要]：A hitherto undescribed satellite DNA family (AvaII satDNA) has been isolated and characterised in Eumeces schneideri, a squamate reptile belonging to the family Scincidae. AvaII satDNA is characterised by a monomer length of 208 bp, a GC content of 59% and exhibits a certain degree of CpG methylation. FISH experiments with AvaII satDNA probe produced bright signals (i) at the end of the short arms of all subtelocentric chromosomes except for pair 14, in which the signal was at the end of the long arms, (ii) at the ends of both arms of the small metacentric chromosomes 12, and (iii) in a terminal position on the acrocentric chromosomes 11 and 13. AvaII satDNA repeats were not found in the metacentric pair 3, whereas only a weak interstitial signal occurred in the metacentric pairs 1 and 2. C-banding showed that this satellite represents most of the constitutive heterochromatin in the genome of this skink, and chromomycin A 3 staining produced a clear signal overlapping with the satellite, except for NOR-associated heterochromatin. In addition, quantitative dot blot analysis showed that these repetitive sequences constitute about 3% of the genomic DNA of this lizard. AvaII satDNA sequence analysis revealed the occurrence of short guanine residue stretches for which a function in structural stability of these sequences and a role in recombination with telomeric sequences can be hypothesised. Fibre FISH experiments showed that on some chromatin fibres telomeric sequences and AvaII satellite DNA repeats are intermingled or overlapping. Copyright (C) 2009 S. Karger AG, Basel |
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