The Analysis Of Structure Of Gene And Genome

With the quick progress of the Human Genome Project (HGP), a great amount of DNA sequences has been accumulated. It is the most pressing task for analyzing the sequences at gene and genome levels. In the thesis, We are devoted to discussing two problems: the structural characteristics of genes and genomes.In Chapter I, the HGP is briefly introduced. The development and accomplishment of bioinformatics are traced. The biological knowledge related to study in the thesis is explained.In Chapter II, the structural characteristics of protein-coding genes are studied. The genes in 11 microbial genomes with different G+C contents have been studied. It has been found that the distribution of bases at three codon positions is asymmetric. The statistical results show that the bases and dinucleotides with low contents are just associated with those in the stop codon TGA. The fact results in the conclusion that the bases related to the stop codon TGA are strictly constrained to be used.In Chapter III, the wavelet transform is described. The wavelet transform is a useful tool for studying non-stationary signals. Using the wavelet de-noising techique, the nosing signals are filtered out and the signals of sharp transition are located.In Chapter IV, the isochore structures of human genomes are studied. There is mosaic organization in the genomes of warm-blooded eukaryotes, i.e. the long DNA segments are fairly homogeneous in G+C contents, when compared to the pronounced heterogeneity throughout the entire genomes. The segments are called as isochores. So far identification of isochore boundaries is still not solved satisfactorily by bioinformatics methods. In the thesis, a combined window model is proposed for identification of the boundaries. The G+C contents corresponding to the window are calculated in turn, when a window moves along a DNA sequence. When a small window is selected, the local signals can be derived. When a large window is selected, theglobal information is calculated. Using the wavelet de-noising techique, the isochore boundaries in human genomes are correctly located by combination of the information derived from two scale windows.