ABSTRACT

When Watson and Crick elucidated the double-stranded complementary basepaired helical structure of DNA in 1953, they pointed out that a possible replication mechanism was inherent in its structure. Because the two strands of a DNA molecule are ‘complementary’ in terms of their nucleotide sequence, each can serve as a template for the formation onto itself of a new complementary companion strand when the individual nucleotide strands of the helical DNA molecule separate by unwinding (Figure 3.1). Eventually two pairs of nucleotide strands will arise by this semi-conservative process which, although simple in outline, is complex in its biochemical detail.