What is the result of the actions taken during the primer annealing phase in LCR?

During the primer annealing phase in Ligase Chain Reaction (LCR), the importance of primer specificity is emphasized. The correct choice reflects that even a single nucleotide mismatch between the primer and the target DNA can prevent the ligation step from occurring. This is crucial because the efficiency of the ligation reaction heavily relies on the perfect complementarity of the primers to their target sequences. If a mismatch occurs, the ligase enzyme is unable to form a stable bond between the primers, leading to a failed reaction.

This specificity is particularly significant in applications such as diagnostics, where accurate detection of specific sequences is essential. The rigorous requirement for exact matching during the annealing phase ensures high fidelity in the amplification process, contributing to the overall reliability and accuracy of the LCR technique.

In contrast, the other statements do not accurately reflect the principles of LCR. While ligation of multiple primers can occur in a broader context, it is not a defining feature of the primer annealing phase itself, focusing instead on the thermal stability and compatibility of the annealed primers. Additionally, the generation of detectable RNA or the creation of only full-length products is not characteristic of the primer annealing phase, as these outcomes depend on various factors beyond primer annealing alone.