The DNA molecule is usually found in which structural form in cells?

• A. B-form double helix
• B. Single-stranded linear
• C. Z-form double helix
• D. A-form double helix

Answer: (A)

Verified step by step guidance

1. Understand that DNA can adopt several structural conformations, including A-form, B-form, and Z-form double helices, as well as single-stranded forms.
2. Recall that the B-form double helix is the most common and biologically relevant structure of DNA under physiological conditions in cells.
3. Recognize that the A-form double helix is typically found in dehydrated samples or RNA-DNA hybrids, not usually in normal cellular DNA.
4. Know that the Z-form double helix is a left-handed helix and occurs under certain conditions but is rare in cells.
5. Conclude that the DNA molecule in cells is predominantly found in the B-form double helix structure.