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Updated: Jul 7, 2026

Genotyping Single Nucleotide Polymorphisms in the Mitochondrial Genome by Pyrosequencing
Published on: February 10, 2023
Structural polymorphism exhibited by a homopurine.homopyrimidine sequence found at the right end of human c-jun
Sarika Saxena1, Aparna Bansal, Shrikant Kukreti
1Nucleic Acids Research Laboratory, Department of Chemistry, University of Delhi (North Campus), Delhi 110007, India.
Abstract:
Homopurine.homopyrimidine (Pu.Py) tracts are likely to play important biological role in eukaryotes. Using circular dichroism, UV-thermal denaturation and gel electrophoresis, we have analyzed the structural polymorphism of a 21-bp Pu.Py DNA segment within human c-jun protooncogene 3'-region, a potential target for triplex formation. Results show that below physiological pH and in the presence of Na+/K+ with Mg2+ the duplex is destabilized/disproportionated, resulting in strand mediated structural transitions to the self-associated structures of G- and C-rich strands separately, identified as G-quadruplex and i-motif species. A significant differential behavior of the monovalent cations was observed, accordingly the presence of Na+ in acidic as well as neutral pH facilitated the duplex formation, while K+ favored the formation of self-associated structures. In Na+ and Mg2+, under acidic and neutral pH conditions, the duplex displayed triphasic and biphasic melting profiles, respectively. This self-association property of oligonucleotides might limit their use as duplex targets in triplex formation. Study is also relevant for understanding structural and biological properties of DNA sequence containing homopurine tracts.
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