arXiv subjects

Chang-Heng Chang

Publications and source records attributed to Chang-Heng Chang.

2 recordsLinked to original sources

arXiv2004

Divergence and Shannon information in genomes

Shannon information (SI) and its special case, divergence, are defined for a DNA sequence in terms of probabilities of chemical words in the sequence and are computed for a set of complete genomes highly diverse in length and composition. We find the following: SI (but not divergence) is inversely proportional to sequence length for a random sequence but is length-independent for genomes; the genomic SI is always greater and, for shorter words and longer sequences, hundreds to thousands times greater than the SI in a random sequence whose length and composition match those of the genome; genomic SIs appear to have word-length dependent universal values. The universality is inferred to be an evolution footprint of a universal mode for genome growth.

q-bio.GN↗

arXiv2003

Quasireplicas and universal lengths of microbial genomes

Statistical analysis of distributions of occurrence frequencies of short words in 108 microbial complete genomes reveals the existence of a set of universal "root-sequence lengths" shared by all microbial genomes. These lengths and their universality give powerful clues to the way microbial genomes are grown. We show that the observed genomic properties are explained by a model for genome growth in which primitive genomes grew mainly by maximally stochastic duplications of short segments from an initial length of about 200 nucleotides (nt) to a length of about one million nt typical of microbial genomes. The relevance of the result of this study to the nature of simultaneous random growth and information acquisition by genomes, to the so-called RNA world in which life evolved before the rise of proteins and enzymes and to several other topics are discussed.

physics.bio-ph↗