The strand of DNA called the leading strand is orientated in the 3' 5' direction towards the replication fork. The lagging strand is orientated in 5' 3' direction toward the replication fork. Scientists named the end of the strands according to the carbons in the sugar ring.
DNA polymerase always works in the 3' 5' direction. It replicates the leading strand continuously as helicase enzyme continues unzipping the fork ahead .
The lagging strand is also replicated in the 3' 5' direction but the process is not continuous because the strand faces away (5' 3' direction) from the point where the unzipping of the fork is taking place and so the "tracks" run out and bits of track called Okazaki fragments have to be added to keep the process going on to completion.
