Chapter 10: DNA Replication

Replisome

A complex of proteins—including helicase, primase, DNA polymerase, and SSBs—that carries out DNA replication

Kinetic Proofreading

Proofreading that occurs during DNA synthesis to correct errors immediately after nucleotide incorporation

Holoenzyme

A fully active enzyme composed of multiple protein subunits with different functions

Primosome

A protein complex (including PriA and primase) responsible for synthesizing RNA primers during DNA replication

Okazaki Fragment

Short DNA segments synthesized on the lagging strand during DNA replication

Telomere

Repetitive DNA sequences found at the ends of linear eukaryotic chromosomes, protecting them from degradation

Helicase

Enzyme that unwinds DNA by breaking hydrogen bonds between bases

Topoisomerase IV

Enzyme in bacteria that helps to decatenate (untangle) DNA following replication

DNA Gyrase

A bacterial type II topoisomerase that introduces negative supercoils to relieve torsional stress during replication

DNA Polymerase III

Main enzyme for synthesizing new DNA strands in bacterial replication

DNA Polymerase I

Fills in DNA gaps and removes RNA primers in bacteria; involved in repair and lagging strand processing

Ribonucleotide Reductase

Converts ribonucleotides to deoxyribonucleotides for DNA synthesis

Thymidylate Synthetase

Enzyme that converts dUMP to dTMP, an essential step in DNA synthesis

DNA Ligase

Joins DNA fragments by forming phosphodiester bonds, especially on the lagging strand

Primase

Synthesizes RNA primers to initiate DNA replication

Dam Methylase

Methylates adenines in GATC sequences, involved in mismatch repair and replication regulation in bacteria

Telomerase

Extends the telomeres of eukaryotic chromosomes using an RNA template

ORC (Origin Recognition Complex)

Binds replication origins in eukaryotic chromosomes and initiates the assembly of the replication machinery

Pre-RC (Pre-replicative Complex)

Includes ORC, Cdc6, Cdt1, and MCM; assembles at replication origins to license DNA replication

MCM Complex

Acts as the helicase in eukaryotic replication to unwind DNA

DNA Polymerase α

Initiates DNA replication by synthesizing short RNA-DNA primers

DNA Polymerase ε

Synthesizes the leading DNA strand in eukaryotes

DNA Polymerase δ

Synthesizes the lagging DNA strand in eukaryotes

PCNA (Proliferating Cell Nuclear Antigen)

Sliding clamp that holds DNA polymerase in place during synthesis

Semi-Conservative Replication

Each new DNA molecule consists of one original (parental) strand and one newly synthesized strand.

Theta Replication

Bacterial replication mode where replication forks move bidirectionally around a circular chromosome, forming a theta (θ) shape.

Activity of Quinolone, Trimethoprim, and Sulfonamide

• Quinolone: Inhibits DNA gyrase, blocking replication.

• Trimethoprim: Inhibits bacterial dihydrofolate reductase.

• Sulfonamide: Inhibits synthesis of the folate cofactor