RESUMO
The pUC19 derivative pAL79 contains six tandem repeats of a 30-bp unit sequence. Supercoiled pAL79 molecules show aberrant electrophoretic mobility under acidic conditions, and microscopic analysis suggests pAL79 molecules conform to tight plectonemes when deposited on a substrate under acidic conditions. This may mean that a short inserted DNA sequence affects the global topology of plasmid DNA.
Assuntos
DNA Super-Helicoidal/química , Repetições Minissatélites , DNA Super-Helicoidal/ultraestrutura , Eletroforese em Gel Bidimensional , Plasmídeos/química , Purinas/química , Pirimidinas/químicaRESUMO
The lengths of simple repeat sequences are generally unstable or polymorphic (highly variable with respect to the numbers of tandem repeats). Previously we have isolated a family of minisatellite DNA (GenBank accession AF422186) that appears specifically and abundantly in the genome of yellow fin sea bream Acanthopagrus latus but not in closely-related red sea bream Pagrus major, and found that the numbers of tandem arrays in the homologous loci are polymorphic. This means that the minisatellite sequence has appeared and propagated in A. latus genome after speciation. In order to understand what makes the minisatellite widespread within the A. latus genome and what causes the polymorphic nature of the number of tandem repeats, the structural features of single-stranded polynucleotides were analyzed by electrophoresis, chemical modification, circular dichroism (CD), differential scanning calorimetry (DSC) and electron microscopy. The results suggest that a portion of the repeat unit forms a stable minihairpin structure, and it can cause polymerase pausing within the minisatellite DNA.
Assuntos
DNA Satélite/química , Repetições Minissatélites , Dourada/genética , Animais , Sequência de Bases , Dicroísmo Circular , DNA/metabolismo , Replicação do DNA , DNA de Cadeia Simples/genética , Instabilidade de Microssatélites , Dados de Sequência Molecular , Desnaturação de Ácido Nucleico , Oligodesoxirribonucleotídeos/química , Reação em Cadeia da Polimerase , Taq Polimerase , TemperaturaRESUMO
The lengths of simple repeat sequences are generally unstable or polymorphic; that is, they are highly variable with respect to the numbers of tandem repeats. To determine the structural features that cause such variability, we examined a minisatellite DNA isolated from the yellow fin sea bream Acanthopagrus latus. Electrophoresis, CD spectra, and calorimetric analyses of oligodeoxyribonucleotides comprised of the minisatellite repeat unit suggest a stable secondary structure is formed within the repeat unit.
