3-BASE, 10.5-BASE, 200-BASE AND 400-BASE PERIODICITIES IN GENOME SEQUENCES

The above periodicities are the main hidden oscillating patterns detec ted so far in the genomic sequences. The 3-base periodicity is charact eristic for the protein-coding sequences only. The source of the appro ximately 10.5-base sequence period is twofold. On the one hand, the se quences coding for alpha-helical coiled-coil regions in proteins have the hidden 3.5 aminoacid repeat which appears as 10.5-base periodicity in the nucleotide sequences. On the other hand, deformability of DNA important for its folding in chromatin is facilitated by periodical po sitioning of certain dinucleotides along the sequences, with the perio d close to 10.5 bases. There are some sequence features which are repe ated at approximately 400-base distances, nearly periodically. This is due to the general segmented organization of the genomes, which appea r to have evolved by fusion of genome segments of nearly standard size s, close to typical 350 bases for eukaryotes and 440 bases for prokary otes. Respective half-units (about 200 bases) are also frequently obse rved. (C) 1998 Elsevier Science B.V. All rights reserved.