Features of DNA

Structure of DNA: The main features of the three-dimensional structure of DNA are: DNA is double-stranded, so there are two polynucleotide stands alongside each other. The two strands are wound round each other to form a double helix. The two strands are joined together by hydrogen bonds between the bases. The bases therefore form base pairs, which are like rungs of a ladder. The base pairs are specific. A only binds to T (and T with A), and C only binds to G (and G with C). These are called complementary base pairs. This means that whatever the sequence of bases along one strand, the sequence of bases on the other strand must be complementary to it. (Incidentally, complementary, which means matching, is different from complimentary, which means being nice.)