B-DNA which is right -handed double helix contains ______ base pairs per turn of the helix and each tum is _____ long .

Answer: BSolution: In B-DNA, one turn of the helix has about $10$ nucleotides on each strand of DNA. A turn occupies a distance of about $3.4$ nm ($34\mathring{A}$ or $3.4\times {10}^{-9}m$) so that adjacent nucleotides or their bases are separated by a space of about $0.34nm\left(0.34\times {10}^{-9}m\text{or}3.4\mathring{A}\right)$.