Hybridization to surface-bound oligonucleotide probes: Influence of point defects
Microarray-based genotyping is based on the high discrimination capability of oligonucleotide probes. For detection of Single Nucleotide Polymorphisms (SNPs) single-base discrimination is required. We investigate how various point-mutations, comprising single base mismatches (MMs), insertions and deletions, affect hybridization of DNA-DNA oligonucleotide duplexes. Employing light-directed in situ synthesis we fabricate DNA microarrays with comprehensive sets of cognate point-mutated probes, allowing us to systematically investigate the influence of defect type, position and nearest neighbor effects. Defect position has been identified as the dominating influential factor. This positional effect which is almost identical for the different point-mutation types, is biased from the local sequence environment. The impact of the MM type is largely determined by the type of base pair (either AT or CG) affected by the mismatch. We observe that single base insertions next to like-bases result in considerably larger hybridization signals than insertions next to nonidentical bases. The latter as well as the distinct position dependence could be explained by a kinetic zipper model in which point defects represent a barrier for the rapid closure of the DNA duplex.