Final answer:
Hydrogen bonds between complementary bases in DNA break upon exposure to high temperatures or certain chemicals, a process known as DNA denaturation. These bonds are relatively weak, making them susceptible to such environmental factors, especially when compared to stronger, covalent bonds.
Step-by-step explanation:
What breaks H-bonds between base pairs? The hydrogen bonds between complementary bases are known to break when subjected to increased temperatures or certain chemicals. This process is often referred to as DNA denaturation. In the double helix structure of DNA, hydrogen bonds hold the complementary bases (adenine with thymine, and guanine with cytosine) together. The bond dissociation energy for hydrogen bonds is considerably lower compared to covalent bonds, making them susceptible to disruption through external stresses such as heat or chemical interference.
In the laboratory setting, this principle is applied where heating DNA can cause the two strands to separate into single-stranded DNA (ssDNA). Upon cooling or removal of the denaturants, these hydrogen bonds can reform, allowing the DNA to reanneal into its original double-stranded form. It is also noteworthy that DNA with a higher GC content is more robust due to the triple hydrogen bonding between G and C and thus requires more energy to denature.