AP BIOLOGY

Detailed explanation-1: -DNA polymerases can only add nucleotides to the 3’ end of an existing DNA strand. (They use the free-OH group found at the 3’ end as a “hook, ” adding a nucleotide to this group in the polymerization reaction.)

Detailed explanation-2: -DNA polymerase can only add DNA bases in one direction, from the 5’ end to the 3’ end. One of the new strands of DNA, the leading strand, is made continuously, the DNA polymerase adding bases one by one in the 5’ to 3’ direction.

Detailed explanation-3: -The primase generates short strands of RNA that bind to the single-stranded DNA to initiate DNA synthesis by the DNA polymerase. This enzyme can work only in the 5’ to 3’ direction, so it replicates the leading strand continuously.

Detailed explanation-4: -Primase functions by synthesizing short RNA sequences that are complementary to a single-stranded piece of DNA, which serves as its template. It is critical that primers are synthesized by primase before DNA replication can occur.

Detailed explanation-5: -DNA polymerase is able to add nucleotides only in the 5’ to 3’ direction (a new DNA strand can be only extended in this direction).