Figure 6.1.DNA structure. The purine nucleotides (adenine and guanine) form hydrogen bonds with
the pyrimidine nucleotides (thymine and cytosine, respectively). Nucleotides are strung together
by a sugar phosphate backbone that has an antiparallel orientation (5^0 –3^0 ) to the complementary
base pairs.
6.2. DNA PACKAGING INTO EUKARYOTIC CHROMOSOMES 137