<prompt> About DNA, true is:Two strands are held together by peptide bondsNon-covalent bonds in sugar-phosphate backboneMost common DNA is Z- DNAMelting point of DNA is closely related to cytosine guanine content of DNA  <response>: DNA 2 strands are held together by hydrogen bonds. There are covalent bonds 3-5 phosphodiester bonds in sugar-phosphate backbone. Melting point of DNA is closely related to the cytosine-guanine content of DNA as C G have 3 bonds, as compared to the 2 bonds present between A T. Most common DNA is B- DNA. A single turn of B-DNA about the long axis of the molecule contains 10 bp. The distance spanned by one turn of B-DNA is 3.4 nm 34 Ao. The width helical diameter of the double helix in B-DNA is 2 nm 20Ao. 