The first characterisation of the overall variability of repetitive units in a species reveals unexpected features of satellite DNA.
We investigated the overall variability of the S1a satellite DNA repeats in ten European populations of Rana temporaria by a new procedure that determines the average sequence of the repeats in a genome. The average genomic sequences show that only 17% of the S1a repeat sequence (494 bp) is variable. The variable positions contain the same major and minor bases in all or many of the population samples tested, but the percentages of these bases can greatly vary among populations. This indicates the presence in the species of an enormous number of repeats having a different distribution of bases in these variable positions. Individual genomes contain thousands of repeat variants, but these mixtures have very similar characteristics in all populations because they present the same type of restricted and species-specific variability. Southern blots analyses and sequences of cloned S1a repeats fully support this conclusion. The S1 satellite DNA of other European brown frog species also presents properties indicating the same type of variability. This first characterisation of the overall repeat variability of a satellite DNA in a species has revealed features that cannot be determined by gene conversion and crossing over. Our results suggest that a specific directional process based on rolling circle amplification should play a relevant role in the evolution of satellite DNA.
Feliciello
Isidoro
I
Dipartimento di Medicina Clinica e Sperimentale, Facoltà di Medicina e Chirurgia, Università di Napoli Federico II, Via Pansini 5, I-80131 Napoli, Italy.
Picariello
Orfeo
O
Chinali
Gianni
G
D000818:Animals; D001483:Base Sequence; D019921:Biotinylation; D003001:Cloning, Molecular; D016384:Consensus Sequence; D004276:DNA, Satellite / Q000737:chemistry* / Q000235:genetics*; D019020:Directed Molecular Evolution; D005784:Gene Amplification; D014644:Genetic Variation; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011896:Rana temporaria / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
D004276:DNA, Satellite