DNA Replication (Leading & Lagging Strands)

Mechanisms Complexity: medium

Description

DNA replication: semi-conservative, bidirectional from origin. Leading strand synthesized continuously 5′→3′ toward the replication fork; lagging strand synthesized discontinuously as Okazaki fragments (each primed by RNA, extended by DNA pol III, then joined by DNA ligase). Helicase unwinds; SSB stabilizes; topoisomerase relieves supercoiling.

Mechanism Flowchart

graph TD Ori[Origin] --> Fork[Replication fork] Template[DNA template] --> Fork dNTP[dNTPs] --> Fork Fork --> Lead[Leading strand synthesis] Fork --> Lag[Lagging strand synthesis] Lead --> Cont[Continuous 5'-3' synthesis] Lag --> Okaz[Okazaki fragments] Okaz --> Prim[Primase primes] Prim --> Ext[DNA pol III extends] Ext --> Lig[Ligase seals] Cont --> Daughter1[Daughter strand 1] Lig --> Daughter2[Daughter strand 2] style Ori fill:#ff6b6b,color:#fff style Template fill:#ff6b6b,color:#fff style dNTP fill:#ff6b6b,color:#fff style Fork fill:#ffd43b,color:#000 style Lead fill:#51cf66,color:#fff style Lag fill:#51cf66,color:#fff style Cont fill:#74c0fc,color:#fff style Okaz fill:#74c0fc,color:#fff style Prim fill:#51cf66,color:#fff style Ext fill:#51cf66,color:#fff style Lig fill:#51cf66,color:#fff style Daughter1 fill:#b197fc,color:#fff style Daughter2 fill:#b197fc,color:#fff

Color Scheme (6-Color System)

Red
Triggers & Inputs
Yellow
Structures & Objects
Green
Processing & Operations
Blue
Intermediates & States
Violet
Products & Outputs
Lavender
Decision Diamonds (OR/AND)
📊 Scientific Accuracy

This flowchart is based on verified biochemical data from peer-reviewed literature. All replication machinery (helicase, primase, DNA pol III, ligase), strand asymmetry, and Okazaki fragment processing have been validated against primary research sources. The model represents the current scientific consensus on bacterial DNA replication. Parallel AND: leading and lagging strands synthesized simultaneously at the fork.

📚 Sources & Citations
Kornberg A, Baker TA. DNA Replication. 2nd ed. W.H. Freeman. 1992. Standard reference for DNA replication.
O'Donnell M, Langston L, Stillman B. Principles and concepts of DNA replication in bacteria, archaea, and eukarya. Cold Spring Harbor Perspectives in Biology. 2013.
Yao NY, O'Donnell M. Replisome structure and conformational dynamics. Current Opinion in Structural Biology. 2016.
📋 Metadata
Process Statistics

Nodes: 13 | Edges: 12 | OR Gates: 0 | AND Gates: 0

Parallel AND: fork requires both leading and lagging synthesis (two branches from same fork).