Which of the following statements is true regarding the genetic material in cells?

The statement indicating that DNA is composed of an alternating sugar-phosphate backbone and bases is accurate because it reflects the fundamental structure of a DNA molecule. In DNA, the backbone consists of alternating sugar (deoxyribose) and phosphate groups, which provide support and stability to the overall structure. Attached to the sugar molecules are nitrogenous bases (adenine, thymine, cytosine, and guanine), which are crucial for encoding genetic information. This arrangement is designed to allow the bases on one strand to pair with complementary bases on the opposite strand, thus forming the characteristic double helix structure of DNA.

In contrast, while DNA does contain various bases, the configuration described in the other options does not align with the structure of nucleic acids: DNA can exist in both double-stranded and single-stranded forms under certain conditions, it is found not just in the nucleus but also in mitochondria (in eukaryotic cells), and although most DNA is double-stranded in cellular conditions, there are scenarios, such as during replication or certain viruses, where DNA can be single-stranded.