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#lagging strand

4 public questions tagged with this topic.

Which of the following enzymes is responsible for synthesizing the lagging strand during DNA replication?

DNA polymerase III synthesizes the lagging strand in short Okazaki fragments during DNA replication. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.

Okazaki fragments are formed on

Okazaki fragments, 1000 to 2000 nucleotides long in bacteria and 100 to 250 in eukaryotes, are short nascent DNA segments observed during brief pulse labeling experiments. They appear exclusively on lagging strand because its template synthesized opposite to fork movement. Each fragment begins with 10 to 12 nucleotide RNA primer made by primase that provides essential 3' OH for Pol III extension. Polymerase extends until reaching previous fragment then displaces or awaits processing. Leading strand shows no such fragments under normal physiological conditions.

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 5: Okazaki fragments on lagging strand

Lagging strand synthesis is

Both template strands are antiparallel, but replication fork moves unidirectionally. Leading strand polymerase follows helicase smoothly synthesizing continuously. Lagging strand template runs 5' to 3' toward fork, requiring polymerase to synthesize away from fork advancement. As helicase unwinds parental duplex, new single-stranded DNA exposed discontinuously behind fork. Primase synthesizes short RNA primers at intervals, Pol III extends each into Okazaki fragment that later becomes processed and joined. This semi-discontinuous mode elegantly solves antiparallel constraint without violating fundamental 5' to 3' polymerization chemistry.

Ref: NCBI Bookshelf, Molecular Cell Biology, Lodish, Figure 11-21: Discontinuous synthesis of lagging strand