ABSTRACT
Various types of repeat sequences are abundant in genomic sequences, and they are associated with the biological phenomena at distinct levels. In particular, comparative analyses of whole-genome-sized sequence data have revealed that repeat sequences cause segmental duplications, which are a type of chromosomal structural arrangement. In this study, we analyzed the relationships between segmental duplications and repeat sequences in human chromosome 7. For this purpose, three methods for detecting repeat sequences were applied to the genomic sequences of human chromosome 7: RepeatMasker for the dispersed repeats, TRF for the tandem repeats, and STEPSTONE for the inter-spread repeats. By plotting the detected repeat sequences against the locations on the chromosome, all three types of repeats were found to be concentrated around the regions of segmental duplications, as a macroscopic feature of their distributions. Furthermore, the latter two repeat sequences were classified in terms of their periods, and the distribution bias of the detected repeat sequences was statistically tested between the segmental duplication regions and the other regions. As a result, the periods of two repeats were biased, with less than a 5% level of significance probability by the chi(2) test, and the repeats with long periods, about 130bp and more than 400bp, were attributed to a bias with a 5% level of significance probability by the normalized residual test. The mechanism of segmental duplications is discussed based on the present results.
Subject(s)
Chromosomes, Human, Pair 7 , Computational Biology , Gene Duplication , Tandem Repeat Sequences , Base Composition , Base Sequence , Chi-Square Distribution , Chromosome Mapping , Cytosine/chemistry , Genome, Human , Guanine/chemistry , Humans , Sequence Homology, Nucleic AcidABSTRACT
UNLABELLED: We constructed a website for inferring a network by applying the graphical Gaussian model, from a large amount of data, including redundant information. The available tools on the website are based on a system, named ASIAN (Automatic System for Inferring A Network), in combination with the two methods in our previous papers, which were designed to analyze gene expression profiles on a genomic scale. One of the remarkable features of the website is its ability to infer a network, concomitant with hierarchical clustering and the following estimation of cluster boundaries. AVAILABILITY: http://eureka.ims.u-tokyo.ac.jp/asian
Subject(s)
Gene Expression Profiling/methods , Gene Expression Regulation/physiology , Internet , Models, Biological , Proteome/metabolism , Signal Transduction/physiology , User-Computer Interface , Computer Simulation , Models, StatisticalABSTRACT
Various types of periodic patterns in nucleotide sequences are known to be very abundant in a genomic DNA sequence, and to play important biological roles such as gene expression, genome structural stabilization, and recombination. We present a new method, named "STEPSTONE", to find a specific periodic pattern of repeat sequence, inter-spread repeat, in which the tandem repeats of the conserved and the not-conserved regions appear periodically. In our method, at first, the data on periods of short repeat sequences found in a target sequence are stored as a hash data, and then are selected by application of an auto-correlation test in time series analysis. Among the statistically selected sequences, the inter-spread repeats are obtained by usual alignment procedures through two steps. To test the performance of our method, we examined the inter-spread repeats in Mycobacterium tuberculosis and Zamia paucijuga genomic sequences. As a result, our method exactly detected the repeats in the two sequences, being useful for identifying systematically the inter-spread repeats in DNA sequence.
Subject(s)
DNA/genetics , Genome , Repetitive Sequences, Nucleic Acid , Algorithms , Base Sequence , DNA/chemistry , Genome, Plant , Models, Genetic , Pattern Recognition, Automated , Zamiaceae/geneticsABSTRACT
Three possible causes responsible for the large genome size of a cyanobacterium Anabaena sp. PCC7120 are investigated: 1) sequential tandem duplications of gene segments, genes or genomic segments, 2) horizontal gene transfers from other organisms, and 3) whole-genome duplication. We evaluated the frequency distribution of angles between paralog locations for the possibility 1), the fraction of genes deviated in GC content, GC skew, AT skew and codon adaptation index for the 2) and the gene-configuration comparison of paralogs for the 3). As a result, the possibility 3), the whole-genome duplication, was more reasonable as a molecular cause than the other causes for the large genome size in Anabaena sp. PCC7120. In addition, the whole-genome duplication was supported by the analysis of distribution pattern of protein genes with respect to functional categories.
