The DNA polymerase can polymerize the deoxyribonucleotides in the 5´-3´ direction. As the two DNA strands are antiparellel to each other, the new strand must be formed on the older strand in the opposite direction. The new strand formed continuously in the 5´-3 direction. This strand is known as leading strand. On the other parent DNA, the short DNA strands are synthesized in 5´-3 direction. These short fragments are known as okazaki fragment and these fragments are joined together to give lagging strand. The RNA primer is replaced by deoxyribonucleotide and the gap is joined by the enzyme DNA ligase (Figure 27.2).

Figure 27.2: Replication of DNA.