Distinct frequency-distributions of homopolymeric DNA tracts in different genomes.
The unusual base composition of the genome of the human malaria parasite Plasmodium falciparum prompted us to systematically investigate the occurrence of homopolymeric DNA tracts in the P. falciparum genome and, for comparison, in the genomes of Homo sapiens , Saccharomyces cerevisiae , Caenorhabditis elegans , Arabidopsis thaliana , Escherichia coli and Mycobacterium tuberculosis. Comparison of theobserved frequencies with the frequencies as expected for random DNA revealed that homopolymeric (dA:dT) tracts occur well above chance in the eukaryotic genome. In the majority of these genomes, (dA:dT) tract overrepresentation proved to be an exponential function of the tract length. (dG:dC) tract overrepresentation was absent or less pronounced in both prokaryotic and eukaryotic genomes. On the basis of our results, we propose that homopolymeric (dA:dT) tracts are expanded via replication slippage. This slippage-mediated expansion does not operate on tracts with lengths below a critical threshold of 7-10 bp.
Department of Molecular Biology and CAOS/CAMM Center, University of Nijmegen, Toernooiveld 1,6525 ED Nijmegen, The Netherlands.
K J
KJ
Dechering
K
K
Cuelenaere
R N
RN
Konings
J A
JA
Leunissen
D000818:Animals; D017360:Arabidopsis / Q000235:genetics; D017173:Caenorhabditis elegans / Q000235:genetics; D004247:DNA / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D005057:Eukaryotic Cells; D016678:Genome; D018503:Genome, Protozoan; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000235:genetics; D010963:Plasmodium falciparum / Q000235:genetics*; D011089:Polydeoxyribonucleotides / Q000235:genetics*; D011387:Prokaryotic Cells; D012441:Saccharomyces cerevisiae / Q000235:genetics
D011089:Polydeoxyribonucleotides; C016681:poly(dG).poly(dC); C084838:polydeoxyadenylic acid-polythymidylic acid; D004247:DNA