6. In the DNA double helix, how are the two strands of DNA held together? A. Chemical bonds between base pairs hold the two strands of DNA together. B. Hydrogen bonds between the base pairs hold the two strands of DNA together. C. Hydrogen bonds between sugar groups and phosphate groups hold the two strands of DNA together. D. Chemical bonds between sugar groups and phosphate groups hold the two strands of DNA together.

Nucleic acid structure refers to the structureof nucleic acids such as DNA and RNA. Chemically speaking, DNA and RNA are very similar. Nucleic acid structure is often divided into four different levels: primary, secondary, tertiary and quaternary.

The correct answer is: B) Hydrogen bonds between the base pairs hold the two strands of DNA together.

Explanation:

The structure of the DNA molecule is given by two strands that are antiparallel and form a double helix. These two strands are held together by the hydrogen bonds that form between the nitrogenous base pairs that are located in the inside of the structure. Meanwhile, the sugar-phosphate backbones of the DNA are located on the outside.

Nitrogenous bases only pair with their complementary bases, meaning that adenine bases pair with thymine bases, and guanine bases only pair with cytosine bases.