AP BIOLOGY

Detailed explanation-1: -DNA polymerase only synthesizes DNA in the 5’ to 3’ direction only. The difference between the leading and lagging strands is that the leading strand is formed towards replication fork, while the lagging strand is formed away from replication fork.

Detailed explanation-2: -DNA is always synthesized in the 5’-to-3’ direction, meaning that nucleotides are added only to the 3’ end of the growing strand. As shown in Figure 2, the 5’-phosphate group of the new nucleotide binds to the 3’-OH group of the last nucleotide of the growing strand.

Detailed explanation-3: -The need for accuracy probably explains why DNA replication occurs only in the 5′-to-3′ direction. If there were a DNA polymerase that added deoxyribonucleoside triphosphates in the 3′-to-5′ direction, the growing 5′-chain end, rather than the incoming mononucleotide, would carry the activating triphosphate.

Detailed explanation-4: -Any single strand of DNA/RNA will always have an unbound 5’ phosphate at one end and an unbound 3’ hydroxyl group at the opposite end. DNA is always read in the 5’ to 3’ direction, and hence you would start reading from the free phosphate and finish at the free hydroxyl group.