Mismatched base và độ bền của bắt cặp chuỗi DNA (dna hybridization)

If a mismatched base is located at the end of the probe, the Tm decreases due to the loss of a single AT or GC base pair.

If the mismatch is in the middle of the probe, the effect on the Tm is more dramatic.
While H-bonds are relatively weak, the effect of many H-bonds between complementary sequences (the zipper effect) adds to the stability of the hybrid (Tm). A mismatch in the middle of a short probe has a big effect on the zipper effect, effectively dividing the lenght of the probe in half. The mismatched base acts as a nucleation center for denaturation, thus depressing the Tm more significantly than expected from the simple loss of an AT or GC pair.



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