Question

Explain why DNA replication is more complicated on the lagging strand when compared to the leading strand, and how does this affect the process?

Answer 1

Answer-

According to the given question-

• We know that DNA replication is semiconservative, where each parental strand is used as a template and synthesizes a new complementary strand with the help of DNA polymerase responsible for joining the deoxyribonucleoside 5′-triphosphates to DNA chain.
• DNA is a double-helical structure and arranged as, in antiparallel directions, one arranged in 5’ to 3’ direction and other is in 3’ to 5’ direction.
• DNA replication occurs only in 5′ to 3′ direction.
• DNA Helicases breaks the bond and unwind the parental DNA after that Single-stranded binding protein or SSB attaches to the unwound DNA template and stabilize them.
• So DNA template which is arranged as 3’ to 5’ direction synthesized continuously and are called leading strand while the DNA template strand which is arranged as 5’ to 3’ synthesized in small, and discontinuous DNA pieces and are called lagging strand.
• These small synthesized fragments of DNA are called Okazaki fragments and are joined by DNA ligase.
• The synthesis of the lagging strand occurs in the direction opposite or away (3' to 5' direction) from the growing replication fork created by DNA helicase. Due to the orientation, the replication of the lagging strand is complex than the leading strand which is correctly oriented and where DNA replication is continuous and towards (5' to 3' direction) the replication fork.