DNA Replication: Leading & Lagging Strands — NEET Biology
✅ Asked in NEET 2025In addition to DNA-dependent DNA polymerases, many additional enzymes are required to complete the process of replication with high degree of accuracy. For long DNA molecules, since the two strands of DNA cannot be separated in its entire length (due to very high energy requirement), the replication occur within a small opening of the DNA helix, referred to as replication fork. The DNA-dependent DNA polymerases catalyse polymerisation only in one direction, that is 5'→3'. This creates some additional complications at the replicating fork. Consequently, on one strand (the template with polarity 3'→5'), the replication is continuous, while on the other (the template with polarity 5'→3'), it is discontinuous. The discontinuously synthesised fragments are later joined by the enzyme DNA ligase.
DNA replication proceeds in 5'→3' direction only, making one strand replicate continuously (leading) while the other replicates in fragments called Okazaki fragments (lagging). Students commonly confuse which strand is continuous and why discontinuous replication happens—it's because the 3'→5' template allows continuous 5'→3' synthesis, but the 5'→3' template requires repeated primer binding, creating fragments. DNA ligase joins these fragments. NEET tests this concept repeatedly because it combines directionality, template function, and enzyme action in one mechanism—fundamental to understanding replication accuracy and speed. Remember: the lagging strand is always the one requiring fragmented synthesis.
This paragraph was tested 4 times in NEET.
The lagging strand of DNA is synthesized in short fragments called: (NEET 2025)
Which of the following statement is correct regarding the process of replication in E.coli?
Given below are two statements: (NEET 2022 Phase 2) Statement I: DNA polymerases catalyse polymerisation only in one direction, 5′ → 3′. Statement II: During replication, one strand is continuous, other discontinuous. Choose the correct answer:
During DNA replication, Okazaki fragments elongate: (NEET 2017)
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