title: Complex organization of a cryptic satellite DNA in the genome of the marine invertebrate Rapana thomasiana Grosse (Gastropoda).
abstract: Isopicnic centrifugation in Cs2SO4-Ag+ gradients at pH 7.0 reveals that the genome of the marine snail Rapana thomasiana Grosse (Gastropoda) contains an AT-rich satellite fraction comprising 5% of the DNA. Restriction enzyme analysis shows that the satellite DNA is composed of a number of related subsets arranged in tandem arrays. They have evolved from the segmental amplification of an 1460 bp long monomer unit with a complex inner organization. Most probably, the present basic repeat originates from an ancestral 400-500 bp long sequence in which some insertions and/or deletions have occurred.
mesh_terms: D000818:Animals; D001483:Base Sequence; D002499:Centrifugation, Density Gradient; D004262:DNA Restriction Enzymes; D004276:DNA, Satellite / Q000235:genetics / Q000302:isolation & purification*; D005796:Genes; D012091:Repetitive Sequences, Nucleic Acid; D012908:Snails / Q000032:analysis*
chemical_list: D004276:DNA, Satellite; D004262:DNA Restriction Enzymes