| In the post-genomic era, with the development of informatics and the progress of genome sequencing projects, researches are gradually focused on the function of genes. Organisms are being viewed as an integrated system. The properties emerged in systematic levels are being studied. In this thesis, the fractals of DNA sequences, including the self-similarity structure, are researched with two aspects of full-scale and details, in order to show the fractals of DNA sequences more globally and more exactly.1. In visualizing long DNA sequences, including the complete genomes of several bacteria, language method and the visualization scheme are introduced to express and discuss globally the fractal-like pattern of the complete genomes in the figure of portrait. As a result, the close relation between the fractal-like patterns and the difference in the g, c, a and t contents in the sequences are uncovered.2. The wavelet transform and the segment average Fourier frequency-spectrum are use to inspect the self-similarity. The two parametric methods are proposed to characterize the self-similarity properties, and mainly used to estimate and analyze the Hurst coefficient. And the variance of Hurst coefficient on the different scales is discovered. Also, the visible fractals of portrait figure are studied by extending the one dimension wavelet transform into two dimensions and this will provide a relatively reasonable reference to the parameter estimation of fractals in two dimensions. Results show that long-range correlation structure prevails through the entire molecule of DNA, and the strict self-similarity is set up to describe DNA sequences only on the segment of low frequency.3. The software with friendly user interface is designed to make the future work more convenient.The work in this thesis can explain qualitatively the fractals of DNA sequences. At the same time, some new problems and suggestions can be inferred from the research, which can be helpful to future bioinformatics studies.
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