Final answer:
Base pairing and base stacking are two mechanisms that hold the DNA double helix together. Base pairing involves complementary pairing of nucleotide bases on the two strands, stabilized by hydrogen bonds. Base stacking refers to the close stacking arrangement of nitrogenous bases within the helix, providing stability.
Step-by-step explanation:
Base pairing and base stacking are two key mechanisms that hold the double helix of DNA together. Base pairing refers to the complementary pairing of nucleotide bases on the two DNA strands, where adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C). These base pairs are stabilized by hydrogen bonds, with A-T forming two hydrogen bonds and G-C forming three hydrogen bonds. This bonding between the bases helps to maintain the structural integrity of the double helix.
In addition to base pairing, base stacking plays a crucial role in holding the double helix together. Base stacking refers to the close stacking arrangement of the nitrogenous bases within the interior of the DNA helix. The nitrogenous bases are stacked on top of each other like the steps of a ladder, with the hydrophobic interactions between the bases providing stability to the helical structure. This stacking interaction, along with the hydrogen bonding between the bases, contributes to the overall strength and stability of the DNA double helix.