Which statement about DNA forms in cells is true?

Which statement about DNA forms in cells is true?

• A. A-DNA is the most predominant form in cells.
• B. B-DNA is the most predominant form in cells.
• C. Z-DNA is the most predominant form in cells.
• D. C-DNA is the most predominant form in cells.

Answer: (B)

Under physiological conditions in living cells, DNA adopts the B form, a right-handed double helix with about 10 base pairs per turn. This shape is the most stable and best suited for the rapid base pairing and interactions with cellular enzymes that drive replication, transcription, and repair. The B form has a well-defined major groove and minor groove, which proteins recognize when binding to DNA. A-DNA, in contrast, is favored in dehydrated or chemical-altered environments and is more compact, with about 11 base pairs per turn. It is not the form typically found in normal cellular conditions. Z-DNA is a left-handed form that can arise in sequences with alternating purine-pyrimidine bases (like CG repeats) under certain conditions such as high salt or strong negative supercoiling; it is relatively rare and not the standard form seen in cells. C-DNA is not a commonly observed form in living cells. So, the statement describing the B form as the predominant DNA structure in cells is true.

Under physiological conditions in living cells, DNA adopts the B form, a right-handed double helix with about 10 base pairs per turn. This shape is the most stable and best suited for the rapid base pairing and interactions with cellular enzymes that drive replication, transcription, and repair. The B form has a well-defined major groove and minor groove, which proteins recognize when binding to DNA.

A-DNA, in contrast, is favored in dehydrated or chemical-altered environments and is more compact, with about 11 base pairs per turn. It is not the form typically found in normal cellular conditions. Z-DNA is a left-handed form that can arise in sequences with alternating purine-pyrimidine bases (like CG repeats) under certain conditions such as high salt or strong negative supercoiling; it is relatively rare and not the standard form seen in cells. C-DNA is not a commonly observed form in living cells.

So, the statement describing the B form as the predominant DNA structure in cells is true.