Question

Two samples of DNA, A and B have melting temperatures $\left( {{T_m}} \right)$ $340$ and $350{\text{K}}$ respectively. Can you draw any conclusion from these data regarding their base content?

Answer 1

To answer this question, you must recall the factors in the structure of DNA molecules that affect the melting points of the DNA samples. Hydrogen bonding between the molecules increases its melting and boiling points.

Complete step by step answer:
It is given in the question that A and B have melting temperatures $340$ and $350{\text{K}}$ respectively.The base pairs present in DNA samples are guanine cytosine base pair (GC base pair) and adenine thymine base pairs (AT base pair).
We know that the GC base pair has 3 hydrogen bonds while the AT base pairs have 2 hydrogen bonds.Also we know that hydrogen bonding leads to increase in the melting points. Thus, more the extent of hydrogen bonding, more is the melting temperature of the sample. The GC base pair leads to more increase in the melting temperature than AT base pair.
Since the melting point of B is higher than A, therefore we can say that the B has a higher GC base pair content as compared to A. While A has a higher AT base pair content than B.

Note:
The melting of DNA is also known as denaturation of DNA. This process is used to analyze various aspects of the base contents in DNA. By comparing the melting temperatures of two genomes, we can estimate the amount of cytosine and guanine.
It is also used in molecular biotechnology, mainly in polymerase chain reaction. The melting temperatures of DNA can be used to equalize the hybridization strengths of a set of molecules.