Which of the following best describes the structure of DNA?

• A. A double helix with strands running in the same direction
• B. A triple helix with strands running parallel
• C. A single-stranded helix with uniform width
• D. A double helix with two strands running in opposite directions

Answer: (D)

Verified step by step guidance

1. Understand that DNA is a molecule that carries genetic information in living organisms and is composed of two strands that form a double helix.
2. Recognize that the double helix structure of DNA was discovered by James Watson and Francis Crick, with the help of Rosalind Franklin's X-ray diffraction images.
3. Each strand of the DNA double helix is composed of nucleotides, which include a sugar (deoxyribose), a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine).
4. The two strands of DNA run in opposite directions, which is referred to as antiparallel orientation. This means one strand runs in a 5' to 3' direction, while the other runs 3' to 5'.
5. The nitrogenous bases on each strand pair specifically (adenine with thymine and cytosine with guanine) through hydrogen bonds, maintaining a uniform width of the double helix.