DNA Replication. Flow Chart.

DNA Replication.

DNA replication occurs at origins of replication.

An enzyme called helicase separates the two strands - separates the H bonds between base pairs.

DNA Polymerase reads the base sequence on each DNA strand and adds corresponding bases to create new strands.

The DNA Polymerase adds new bases in a 5' to 3' direction as bases are joined at the free OF group at the 3' end of the newly synthesised strand. On one strand as the DNA is unzipped, new bases can be added continuously and this is called the leading strand. The other newly created strand can only be synthesised in small pieces in a 5' to 3' direction as the parent strand is unzipped. This is called the lagging strand.

The small fragments in the lagging strand (called Okazaki fragments) are joined by an enzyme called DNA ligase. The two new strands are made up of half the original parent strand and half the newly synthesised strand.