Final answer:
The DNA molecules with lower Guanine-Cytosine content have a lower melting temperature because they form fewer hydrogen bonds, thus requiring less heat to denature, compared to DNA with higher G=C content. The melting temperature reflects the stability of the DNA double helix and its tendency to separate into single strands.
Step-by-step explanation:
The melting temperature of DNA is influenced by the base pair content of the DNA strands. Two DNA molecules with lower Guanine-Cytosine (G=C) content will have a lower melting temperature compared to DNA with a higher G=C content. This is because G=C base pairs form three hydrogen bonds with each other as opposed to the Adenine-Thymine (A=T) pairs which form only two hydrogen bonds. So, more G=C content leads to a higher melting temperature. The melting temperature is a critical indicator of how strongly the two strands of DNA can bind to each other, and is measured at the point where the DNA is denatured to about 50%.
During denaturation, the DNA double helix unwinds and the strands separate as the temperature rises. Annealing occurs when the separated strands cool and form hydrogen bonds once again with complementary sequences, which can be natural sequences or laboratory designed primers. The ease of this separation and re-joining is primarily dependent on the G=C versus A=T ratio within the DNA.