XVI International Botanical Congess

An eukaryotic genome containing unique and moderately repeating sequences also contains tandemly arranged multiply repeating ones termed satellite DNA. They are known to be located in the constitutive heterochromatin areas of the chromosomes defining in a way their compact structure. When a bend appears in a monomer of satellite DNA, due to regular repeating organization the long chains ought to reveal a tertiary structure. Computer modeling has proved that such molecules have to be of a solenoid form termed coiled double helix (CDH-form).In our study the primary structure of the Citrus ichangensis satellite DNA repeating unit has been estimated. A hexamer of the repeating unit of C. ichangensis satellite DNA was cloned. Polyacrylamide gel electrophoresis at different temperature demonstrated that the shape of cloned hexamer is other than linear. An electron microscopic analysis revealed small diameter circles in the hexamer under analysis. Satellite DNA of other citric plants was characterized. Bending behaviour of the repeats revealed structural conservation although the nucleotide sequence varied considerably among species.