DNA Replication

Nucleotide

building blocks of DNA

• phosphate

• deoxyribose sugar

• base

Pyrimridines

• Cytosine (C)

• Thymine (T)

Purines

• Adenine (A)

• Guanine (G)

DNA Structure

• Double helix

• Sugar-phosphate backbone

• Antiparallel strands

  • (3’ to 5’ and ‘5’ to 3’)

• Complementary base pairing (hydrogen bonds)

• Major groove & minor grove

• Double stranded

Semi Conservative Replication

a process where each new DNA molecule is made of one original (parent) strand and one newly made strand

• need to be antiparallel

DNA Polymerase

enzyme that builds new DNA strands by adding nucleotides to a growing chain during DNA replication

• synthesizes DNA in a 5’ to 3’ direction

DNA Pol 3

does bulk of DNA replication

DNA Pol 1

• involved in replication on lagging strand

• can remove RNA primer

• has 5’-3’ exonuclease activity

Exonuclease

enzyme that finds mistake coming 3’-5’ and allows for DNA pol to fix

oriC

the specific DNA sequence in bacteria where DNA replication begins

ter

a specific DNA region where replication ends in bacteria

Single-Stranded Binding Proteins

protein that binds to separated DNA strands to keep them from rejoining during replication

DNA B helicase

an enzyme that unwinds the DNA double helix by breaking hydrogen bonds between the two strands during replication

Leading Strand

the DNA strand that is synthesized continuously in the same direction as the replication fork moves

• only has primer laid down at oriC

Lagging Strand

the DNA strand that is synthesized in short segments (Okazaki fragments) in the opposite direction of the replication fork movement

Ozaki fragments

short pieces of DNA that are made on the lagging strand during DNA replication and later joined together

RNA primer

short RNA sequence that provides a starting point for DNA polymerase to begin DNA synthesis

Primase

an enzyme that makes short RNA primers needed to start DNA replication

DNA ligase

enzyme that joins Okazaki fragments by sealing the sugar-phosphate backbone

DNA Gyrase

relaxes supercoils ahead of replication fork

Topoisomerase II

enzyme that cuts both DNA strands to relieve twisting and then reattaches them during replication