Final answer:
The melting temperature (Tm) of DNA is influenced by the GC content due to the number of hydrogen bonds, not the percentage of purines. The statement in the question is false.
Step-by-step explanation:
The Tm (melting temperature) of a DNA double-stranded molecule is not a direct result of the percent of purines in the DNA, but rather the number and strength of hydrogen bonds between the base pairs. In DNA, adenine (A) pairs with thymine (T) via two hydrogen bonds, and cytosine (C) pairs with guanine (G) via three hydrogen bonds. Because G-C pairings are held together by three hydrogen bonds compared to A-T's two, DNA with a higher GC content will have a higher Tm due to the greater strength of the additional hydrogen bonds. Therefore, the statement is false; the Tm is more directly related to the G-C content rather than the proportion of purines (A and G).