If a probe and target are 100% identical, what is the ideal stringency condition for the wash?

When a probe and its target are 100% identical, a high stringency wash condition is ideal. High stringency washing conditions typically involve higher temperatures and potentially higher salt concentrations, which help to ensure that only perfectly matched probe-target hybrids remain bound. This minimizes the likelihood of non-specific binding and increases the accuracy of detecting the target of interest.

In this scenario of perfect complementarity, high stringency conditions ensure that any weak or partially matched sequences are effectively washed away, providing clearer and more reliable results. This is particularly important in molecular biology applications such as hybridization assays, where the specificity and sensitivity of the probe can greatly influence the outcomes.

In contrast, low stringency conditions, which involve lower temperatures and salt concentrations, allow for some mismatched pairs to remain bound. This scenario would not be appropriate when you know the probe and target are perfectly identical, as it could lead to false positives or ambiguous results. The terms "no stringency" and "variable stringency" further dilute the specificity of the binding interactions, making them less suitable as well. Thus, high stringency is the most appropriate choice in this context.