Question

The enzyme DNA polymerase works only in the 5′ to 3′ direction. How does this affect the leading strand and the lagging strand?

Answer 1

Answer:

B

Explanation:

DNA replication is semiconservative- meaning the old template strand will form a double helix with the newly synthesized strand. The DNA polymerase can only replicate DNA in the 5’ -> 3’ direction on a DNA strand. However, because the two strands of a DNA double helix run antiparallel (and they are replicated together), then during replication, one strand will be oriented in the opposite direction (i.e 3’ -> 5’ direction).

Because DNA polymerase requires a primer to begin replication, the leading strand will require one primer, because replication on this strand occurs continuously. On the lagging strand, many primers are required because replication is done piecemeal forming fragments called Okazaki fragments. The fragments are later joined by DNA ligases.