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[摘要]：Human ribosomal intergenic spacer (rIGS) contains in its central part two highly homologous 2 kb repeats. LR1 and LR2. In this paper, we investigate heterogeneity of the variable LR2 segment (LR2(var)) in the human rIGS. More than 500 LR2(var) copies from ten unrelated human genomes have been cloned and sequenced. Prolonged (G)(n) (AG)(m) compound microsatellite clusters with 'n' and 'm' notions fluctuating in random manner span central parts of almost all LR2(var) variants. Nucleotide sequences flanking the central microsatellite clusters are represented by more than 30 structural groups, with the two major (A and B) and six minor (C-H) ones. The analysis of sequencing data let us propose that the LR2(var) variability can be derived by various ways, including microsatellite DNA slip-strand mispairing during replication, non-equal crossover and segmental DNA exchange between LR1(var) and LR2(var) through the mechanism of gene conversion. (c) 2008 Elsevier B.V. All rights reserved. |
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