Most commonly as a double-stranded helix comprising two complimentary molecules held together by hydrogen bonds, this is commonly called "dsDNA" (double-stranded DNA).<ref>Single-stranded DNAs (ssDNA) do exist in certain [[bacteriophage]]s, however they cannot be replicated without first creating the complimentary strand to use as a template.</ref> The [[nucleotide]]s which are the "building blocks" of DNA have three main parts: A nitrogenous base (the "letters" in the sequence), a [[sugar]], and a [[phosphate]] group. When nucleotides are joined into DNA strands, they form a chain with the phosphate group of one nucleotide binding to the ribose of the next. | Most commonly as a double-stranded helix comprising two complimentary molecules held together by hydrogen bonds, this is commonly called "dsDNA" (double-stranded DNA).<ref>Single-stranded DNAs (ssDNA) do exist in certain [[bacteriophage]]s, however they cannot be replicated without first creating the complimentary strand to use as a template.</ref> The [[nucleotide]]s which are the "building blocks" of DNA have three main parts: A nitrogenous base (the "letters" in the sequence), a [[sugar]], and a [[phosphate]] group. When nucleotides are joined into DNA strands, they form a chain with the phosphate group of one nucleotide binding to the ribose of the next. |