The nucleotide composition and pyrimidine clusters in DNA from beef heart mitochondria

Abstract

Study of primary structure of mitochondrial DNA (mtDNA) helps elucidate the general problem of DNA specificity and the numerous questions pertaining to the origin, evolution and functions of this nucleic acid. What we know so far about the composition of mtDNA have been derived from p and T, determinations [ 11. We have very scanty knowledge about the presence, nature and distribution pattern of minor bases in mtDNA. We have detected a small DNA-methylase activity in a mitochondrial fraction from loach embryos. It was an indication that animal mtDNA may in principle be methylated [2]. A nearest-neighbour base sequences possess unique mtDNA from slime mould [3] and determination of pyrimidine clusters frequencies in yeast mtDNA [4] showed that their nucleotide sequences possess unique specific features. This may have aroused interest to studying mtDNA; however, no such information has come to our notice, especially with respect to animal mtDNA. This paper reports the results of a comparative study of the nucleotide composition (CC content), of the methylation character and the degree of pyrimidine clustering in DNA from beef heart mitochondria and nuclei.