Questions and Answers
What type of DNA damage is primarily caused by exposure to ultraviolet light?
Which repair mechanism is most effective for repairing double-strand breaks in DNA?
Which consequence is most commonly associated with uncorrected DNA base modifications?
What is the primary cause of single-strand breaks in DNA?
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Which type of DNA damage is effectively corrected by nucleotide excision repair mechanisms?
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What consequence is most likely when DNA repair mechanisms fail to correct oxidative damage in DNA?
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Which of the following types of DNA damage would most likely result in chromosomal instability if left unrepaired?
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In relation to DNA damage, what repair mechanism is primarily associated with fixing base modifications caused by chemicals?
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Which DNA repair mechanism is involved in correcting bulky DNA adducts that can be caused by environmental carcinogens?
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What is the primary consequence of unrepaired mismatches in DNA during replication?
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Study Notes
Types of DNA Damage
- Single-strand breaks (SSBs): Disruption of one DNA strand; can lead to replication issues and genome instability.
- Double-strand breaks (DSBs): Breaks that affect both strands; severely impacts genetic integrity and can lead to chromosomal rearrangements.
- Base modifications: Alteration of DNA bases due to factors like oxidation or alkylation; can result in incorrect base pairing and mutations during replication.
- Crosslinking: Covalent bonds formed between DNA strands, inhibiting replication and transcription; linked to cancer and cell death.
- Thymine dimers: Formation of covalent bonds between adjacent thymine bases due to UV radiation; causes distortion of DNA structure and blocks replication.
- Interstrand crosslinks (ICLs): Bonds between opposite strands of DNA; impede DNA replication and transcription, potentially triggering cell cycle arrest.
Consequences on Genetic Integrity
- DNA damage can lead to mutations, which may insert, delete, or change nucleotides, disrupting gene function.
- Accumulation of DNA lesions can trigger apoptosis or senescence, reducing cell proliferation.
- Repair failure can result in hereditary diseases, cancer, and genomic instability.
- Chronic DNA damage response might cause inflammation and tissue degeneration.
Repair Mechanisms
- Base Excision Repair (BER): Fixes small, non-helix-distorting base lesions; replaces damaged bases without affecting the DNA backbone.
- Nucleotide Excision Repair (NER): Targets bulky DNA adducts and UV-induced lesions; removes a short stretch of DNA surrounding the damage.
- Homologous Recombination (HR): Repairs DSBs accurately using a homologous template; crucial during the S and G2 phases of the cell cycle.
- Non-Homologous End Joining (NHEJ): Joins broken DNA ends directly; quick but prone to errors, often leading to mutations.
- Mismatch Repair (MMR): Corrects replication errors that escape proofreading; maintains genetic stability by fixing base-pair mismatches.
- Translesion Synthesis (TLS): Allows bypass of DNA lesions during replication; can introduce mutations but helps avoid replication fork collapse.
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Description
This quiz explores the various types of DNA damage and their consequences on genetic integrity. It also correlates different types of DNA damage with their respective repair mechanisms, enhancing the understanding of DNA resilience and repair processes.
