The Character Of Sequence In Translation Start Region And The Correlation Properties Among Genes In Prokaryote

The paper is composed of three chapters:In the first chapter, based on the first ATG rule, the distance from L-Ter to the start codon and that from L-Ter to the ATG downstream next to the start codon are analyzed for certain genes and theoretic forecast genes. The results show that the distance from L-Ter to the start codon mainly distributes in range of 20 amino acids; Among the genes with the start codon of the first ATG and first GTG, the average distance between L-Ter and the ATG downstream adjacent to the start codon is 4-5 times of that between L-Ter and the start codon. These may be a character of the start codon. Meanwhile, the property shows the reason why minority genes start with GTG. As for the genes disobeying the first ATG and first GTG rule, their appearance rates of ATG > GTG and TTG between L-Ter and the start codon are analyzed .The rates in certain genes are very different from that in theoretic forecast genes for E.coli.In the second chapter, we describe the character intensity of SD sequence by using information clustering and analyze SD sequences for 551 documented operonsfrom E. coli (each with at least two genes). A significant positive correlation of the predicted SD sequence and operons structure gene expression level respectively was ascertained. Such that genes within operons have the stronger SD sequence than initial genes, and the number of SD sequence intensity is positively correlated to the gene expressed level. After studying the distance distribution between L-Ter and the start codon for genes with an SD sequence and without an SD sequence in E.coli, and for genes in c-elegans genome and in yeast genome, and after studying the distance distribution between terminator mode and the start codon in start codon upstream, consider SD sequence causes the two peaks of distance distribution between L-Ter and the start codon, and find that the two peaks gradually disappear with the evolution of biology (from prokaryote to simple eukaryotic), the disappearance of the character of SD sequence in eukaryotic shows evolution result.In the third chapter, Codon Adaptation Index (CAI) parameter can be used to measure the character of the gene expression level. The correlation properties between two genes are calculated by using information-theoretic method. After analyzing the Relative Frequency of 6-gene modes, 4-gene modes and 3-gene modes, the results show: there is both strong correlation and great RF values for the segments that are composed of the same expression level genes. The segments which mainly consist of opposite expression level genes have the stronger correlation but the lower RF values.