Final answer:
Hydrogen bonds and van der Waals interactions are primarily responsible for stabilizing the hydrogenous bases in DNA, with hydrophobic interactions also playing a role in maintaining the helical structure.
Step-by-step explanation:
The interactions responsible for holding the nitrogenous bases together stacked one on top of another in the center of a DNA molecule, and contributing to the stability of the whole DNA molecule are primarily hydrogen bonds and van der Waals interactions. While hydrogen bonds form between complementary bases such as adenine (A) with thymine (T), and cytosine (C) with guanine (G), providing the specificity and strength of association within the DNA molecule, it is the stacking of these bases and their hydrophobic interactions, also enhanced by van der Waals forces, that further stabilize the DNA structure. These interactions are critical as they contribute to the DNA’s ability to maintain a uniform helical shape and its overall stability.