NUCLEOTIDE FREQUENCY MAP - A NEW TECHNIQUE FOR PICTORIAL REPRESENTATION OF DINUCLEOTIDE FREQUENCIES

In this communication, a method of presentation of dinucleotide freque ncies in the form of a contour diagram (mao), designated as dinucleoti de frequency map (DNFM), has been used for the first time to analyse t he compositional bias of different nucleic acid sequences, Such maps p rovide a method of visualization of the nucleotide usage at a glance a nd allow simultaneous representation and comparative analysis of multi ple sequences of different origins, Using the technique of DNFMs, it h as been shown that the dinucleotide frequency distribution profile of any nucleotide sequence often exhibits distinct statistical bias, whic h is not predictable from the knowledge of its base composition, Analy sis of bacterial rDNA operons showed that 16S and 23S rRNA genes of su ch species, in general, follow similar dinucleotide patterns, which ar e different from those of the intervening regions, The technique of DN FM has also been applied to analyse the compositional heterogeneity of the genomic sequence of the bacteriophage lambda to show that the din ucleotide frequencies vary along the phage genome depending on the dis tribution of open reading frames.