In terms of stringency, what does high temperature and low salt result in?

High temperature and low salt concentration lead to more stringent conditions during nucleic acid hybridization. Stringency refers to the conditions under which two nucleic acid strands are allowed to hybridize. When the temperature is elevated, it increases the kinetic energy of the molecules, causing more unstable interactions between mismatched bases. This makes it less likely for DNA or RNA strands that do not have perfect complementarity to remain hybridized.

Low salt concentrations further contribute to increased stringency because salt stabilizes the negative charges present on the phosphate backbone of nucleic acids. In a low salt environment, there is reduced shielding of these charges, resulting in weaker interactions and diminished ability for non-complementary or partially complementary sequences to hybridize effectively.

Therefore, when both high temperature and low salt are applied, only sequences with a high degree of complementarity are likely to remain bound, thus ensuring that the binding conditions are more stringent. This is crucial in applications such as PCR and Southern blotting, where specificity of hybridization is paramount to obtaining accurate results.