[Detection and several characteristics of leach genome palindromes].

Abstract

About 5% of the loach (Misgurnus fossillis L.) DNA reassociates at Cot values virtually equal to zero. 50% of the reassociate are resistant to nuclease S1 treatment and reveal the properties of double-stranded structure when chromatographed on hydroxyapatite. Some proofs of palindromic (hair-pin) nature of this fraction have been obtained. An introduction of nicked scissions into the palindromic DNA by pancreatic DNAse treatment under pessimal conditions made it possible to investigated reassociation kinetics of the nucleotide sequences forming palindromes. Two different types of nucleotide sequences appeared to exist in the palindromic fraction with repetition frequencies (ni) equal to 3 X 10(2) and about 1. Homologies were revealed between these sequences and the fraction of corresponding repetition frequency of the main part of the genome. Adjacent sequences contain repetitive regions with ni equal to 10(5) and 5 X 10(3). On the basis of the data obtained some conclusions were made about the distribution of usual and inverted repetitions in the loach genome.