basebasemismatches

Base mismatches, also known as nucleotide mismatches or simply mismatches, are points in a DNA or RNA sequence where a standard base pairing is disrupted. In double-stranded DNA, the standard pairings are adenine (A) with thymine (T) and guanine (G) with cytosine (C). In RNA, thymine is replaced by uracil (U), so A pairs with U and G pairs with C. A base mismatch occurs when a non-standard pairing exists, such as A with G, T with C, or A with C.

These occurrences can arise during DNA replication or repair processes. Errors during replication, where the wrong nucleotide is incorporated, are a common source. If not corrected, these mismatches can lead to mutations. While DNA polymerase has proofreading capabilities to fix many mismatches immediately, some escape detection. Base mismatches are also central to certain biological phenomena. For instance, in the immune system, somatic hypermutation and class switch recombination in B cells involve DNA mismatches that are then processed to introduce genetic diversity.

The study of base mismatches is crucial in molecular biology and genetics. Understanding their formation, detection, and repair mechanisms provides insights into genome stability, disease development, and evolutionary processes. Techniques like mismatch cleavage assays and next-generation sequencing are employed to identify and analyze these genetic variations.