The lagging strand, however, runs in the opposite direction that it was unzipped, making it harder for the DNA polymerase to move down the strand, so it keeps returning to the strand until the job is done. Progress % Practice Now. Paired by weak, base-specific hydrogen bonds between DNA strands. Because the leading strand runs in the same direction that it was unzipped, the DNA polymerase moves with ease down the length of the strand. Proof reader enzymes then run down the strand detecting and fixing errors. 2020 QCE Biology Revision, Revise Queensland QCE Biology Unit 1, 2, 3 and 4, Organic/nitrogenous base that always contains nitrogen. Phosphate groups are attached to the 5′- and 3′-carbon atoms of each sugar to form the backbone chain of DNA. For this essay, it would be much too difficult to discuss the process of cell division, which is the biological basis of life.