Answer:
By hydrogen bonds between nucleotide bases
Explanation:
A DNA molecule is a double-stranded molecule that is informing one structure two strands of nucleotide are involved.
The double-stranded molecule backbone is composed of the phosphate and sugar group and the inside of the backbone are presents the nitrogenous bases. The nitrogenous bases are of four types which are: adenine, cytosine, guanine, and thymine.
These nitrogenous bases are attached according to the Chargaff rule that is adenine binds thymine and cytosine binds guanine. These bases bind with the help of the hydrogen bond as 2 hydrogens participate between adenine and thymine and 3 hydrogens participate between cytosine and guanine.
Thus, hydrogen bonds between nucleotide bases is correct.
