In a double-stranded fragment of DNA, which of the base pairs would you expect to be most stable

To determine which base pairs are most stable in a double-stranded DNA fragment, we need to consider the bonding patterns between the base pairs. In DNA, there are four types of nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T).

The stability of a base pair is primarily determined by the strength of the hydrogen bonds formed between the bases. Adenine pairs with thymine through two hydrogen bonds (A-T), and guanine pairs with cytosine through three hydrogen bonds (G-C).

Since the number of hydrogen bonds between the base pairs differ, G-C base pairs are generally more stable than A-T base pairs. The additional hydrogen bond in G-C pairs contributes to a stronger interaction between the two strands of DNA, leading to increased stability.

Therefore, in a double-stranded DNA fragment, you would expect the guanine-cytosine (G-C) base pairs to be more stable than the adenine-thymine (A-T) base pairs.