DNA Repair Flashcards

Flashcards for DNA Repair Lecture

Spontaneous DNA Damage

Damage resulting from natural processes like hydrolysis, deamination, and tautomeric shifts.

Chemical DNA Damage

Damage caused by exposure to chemicals like alkylating agents, ROS, intercalating agents, and adducts.

Physical DNA Damage

Damage resulting from physical agents such as UV light and ionizing radiation (X-rays, gamma rays).

Replication Errors

Mistakes during DNA replication leading to mismatches, insertions, or deletions.

Direct Repair

DNA repair mechanisms that directly reverse the damage without removing nucleotides (e.g., photoreactivation).

Excision Repair

DNA repair pathways that excise damaged or mismatched nucleotides and resynthesize the DNA (BER, NER, MMR).

Translesion Synthesis (TLS)

A DNA damage response that uses specialized low-fidelity DNA polymerases to bypass replication-blocking lesions.

Recombinational Repair

A DNA repair pathway that uses homologous recombination to repair double-strand breaks.

SOS Response

A bacterial global response to severe DNA damage, inducing DNA repair genes and TLS polymerases.

Hydrolysis (DNA Damage)

Loss of a base from a nucleotide, creating an abasic (AP) site.

Alkylation (DNA Damage)

Addition of alkyl groups to DNA bases or the phosphate backbone, leading to mispairing or strand breaks.

Deamination (DNA Damage)

Removal of an amino group from a base (e.g., cytosine to uracil), altering base pairing.

Pyrimidine Dimers

Covalent linkages between adjacent pyrimidine bases (e.g., thymine-thymine) caused by UV light.

Ionizing Radiation (DNA Damage)

Induces single- and double-strand breaks in DNA and generates ROS, leading to base damage.

Intercalating Agents

Molecules that insert between DNA base pairs, causing insertions/deletions and frameshift mutations.

Base Analogs

Molecules that mimic natural DNA bases and can cause mispairing and transition mutations.

Reactive Oxygen Species (ROS)

Cause oxidative base damage, strand breaks, and mutagenesis in DNA.

Chemical Adducts

Large molecules covalently bound to DNA that distort the helix and block replication/repair.

Transition Mutation

A point mutation where a purine is substituted for a purine (A ↔ G) or a pyrimidine for a pyrimidine (C ↔ T).

Transversion Mutation

A point mutation where a purine is substituted for a pyrimidine (A/G ↔ C/T).

Tautomeric Shifts

Temporary proton shifts in DNA bases that lead to rare tautomeric forms and mispairing during replication.

Photoreactivation Repair

A direct repair mechanism that uses DNA photolyase and blue light to cleave UV-induced pyrimidine dimers.

Alkylating Agents (Effect on DNA)

Add alkyl groups to DNA bases or the backbone, leading to mutagenesis, replication blocks, and strand breaks.

Methyltransferases (DNA Repair)

Enzymes that transfer methyl groups from DNA to their own cysteine residue to repair alkylated bases.

Dioxygenases (DNA Repair)

Enzymes that use Fe²⁺ and α-ketoglutarate to oxidatively demethylate alkylated DNA bases.

UvrABC Nuclease

Enzyme complex involved in NER that detects bulky lesions and makes dual incisions on the damaged DNA strand.

DNA Glycosylase

Enzyme that removes damaged bases from DNA during base excision repair (BER).

APE1 (AP Endonuclease)

Enzyme that cleaves the DNA backbone at AP sites during base excision repair (BER).

Pol β (DNA Polymerase Beta)

DNA polymerase involved in short-patch base excision repair (BER) in eukaryotes.

Nucleotide Excision Repair (NER)

A DNA repair pathway that removes bulky lesions or helix-distorting damage.

Base Excision Repair (BER)

A DNA repair pathway that removes small, non-helix-distorting base damage.

XP Proteins

Proteins involved in nucleotide excision repair (NER) in eukaryotes.

DNA Ligase

Enzyme that seals the nick in the DNA backbone after repair synthesis.

Pol η (DNA Polymerase Eta)

A translesion synthesis (TLS) polymerase that bypasses thymine dimers.

PCNA Ubiquitination

A modification that controls translesion synthesis (TLS) by recruiting specialized polymerases.

MutS (Mismatch Repair)

Protein that recognizes mismatches in DNA during mismatch repair (MMR).

MutH (Mismatch Repair)

Endonuclease that cleaves the unmethylated (new) strand at GATC sites during mismatch repair (MMR).

LexA

Repressor protein that inhibits the expression of SOS repair genes in bacteria.

RecA*

Activated form of RecA protein that triggers the SOS response in bacteria.

UmuD/UmuC

Proteins that form DNA polymerase V, a TLS polymerase involved in SOS repair.

Mismatch Repair (MMR)

A DNA repair system that corrects errors made during DNA replication.

Homologous Recombination (HR)

A major DNA repair pathway for double-strand breaks

DNA Photolyase

An enzyme that reverses pyrimidine dimers in direct repair

O6-methylguanine

A common lesion caused by alkylating agents that can mispair with thymine.

N7-methylguanine

A common lesion caused by alkylating agents

8-oxoG

A type of oxidative DNA damage caused by ROS

AP site

A location in DNA that has neither a purine nor a pyrimidine base

SulA

A protein induced by the SOS response that causes cell division arrest.

Adducts

Substances that bind to DNA and alter its structure.

Pol V

A TLS polymerase that introduces mutations.