Final answer:
DNA denaturation occurs at high temperatures, separating the two strands by breaking hydrogen bonds.
Step-by-step explanation:
Heating DNA causes the two strands of the double helix to separate because the heat disrupts the hydrogen bonds that hold the two strands together. The physical properties of DNA include the characteristic of denaturation, which happens at high temperatures, typically above 80 to 90 degrees centigrade.
During denaturation, the hydrogen bonds and hydrophobic interactions between the bases are disrupted, causing the DNA to lose its double helical structure and the two strands to separate completely. However, the individual strands themselves remain intact because the covalent bonds that hold the atoms.
DNA with higher G=C content requires higher temperatures to denature due to more hydrogen bonding. On cooling or removal of heat, the two strands can anneal, or rehybridize, to form the double helix once again, as long as the sequence conditions allow it.