Biomedical subjects
Publications and source records attributed to Sprizhitsky YuA.
DNA is modelled as a sequence of nucleotide runs. This model is shown to provide a more adequate description of the observed frequencies of occurrence of local homopurine-homopyrimidine mirror repeats than the second-order homogeneous Markov chain model. The procedure is described for estimating the statistical significance of the occurrence of some complex nucleotide combinations in DNA.
A statistical analysis of the occurrence of particular nucleotide runs in DNA sequences of different species has been carried out. There are considerable differences of run distributions in DNA sequences of procaryotes, invertebrates and vertebrates. There is an abundance of short runs (1-2 nucleotides long) in the coding sequences and there is a deficiency of such runs in the noncoding regions. However, some interesting exceptions from this rule exist for the run distribution of adenine in procaryotes and for the arrangement of purine-pyrimidine runs in eucaryotes. The similarity in the distributions of such runs in the coding and noncoding regions may be due to some structural features of the DNA molecule as a whole. Runs of guanine (or cytosine) of three to six nucleotides occur predominantly in noncoding DNA regions in eucaryotes, especially in vertebrates.
A sequence homologous to the known SOS boxes is found in the Po promoter of phage lambda. It is suggested that the sequence found is a binding site for the LexA repressor. The mechanism of the LexA part in regulation of lambda development is discussed. It is based on the competitive transcription of the RNA encoding CII protein and the short OOP-RNA transcribed from the Po promoter.