Podcast
Questions and Answers
Which of the following symptoms is associated with Xeroderma pigmentosum (XP)?
Which of the following symptoms is associated with Xeroderma pigmentosum (XP)?
- Neurological lesions
- Aplastic anemia
- Frequent stomach pain
- Extreme sensitivity to sunlight (correct)
Ataxia telangiectasia (AT) is caused by hypersensitivity to UV light.
Ataxia telangiectasia (AT) is caused by hypersensitivity to UV light.
False (B)
What is the genetic inheritance pattern of Lynch Syndrome (LS)?
What is the genetic inheritance pattern of Lynch Syndrome (LS)?
Autosomal dominant
Individuals with Fanconi's anemia exhibit growth __________________.
Individuals with Fanconi's anemia exhibit growth __________________.
Match the cancer types with their association to Lynch Syndrome (LS):
Match the cancer types with their association to Lynch Syndrome (LS):
Which type of excision repair is responsible for correcting bulky lesions in DNA?
Which type of excision repair is responsible for correcting bulky lesions in DNA?
DNA polymerases have no proofreading activity.
DNA polymerases have no proofreading activity.
What are the potential consequences of mutations that survive DNA replication mistakes?
What are the potential consequences of mutations that survive DNA replication mistakes?
What is one consequence of DNA damage that is not repaired in a timely manner?
What is one consequence of DNA damage that is not repaired in a timely manner?
Base excision repair (BER) primarily corrects damage to ________ bases.
Base excision repair (BER) primarily corrects damage to ________ bases.
Match the following DNA repair processes with their descriptions:
Match the following DNA repair processes with their descriptions:
The process of photoactivation repair is only found in prokaryotic organisms.
The process of photoactivation repair is only found in prokaryotic organisms.
What does DNA Ligase do in the DNA repair process?
What does DNA Ligase do in the DNA repair process?
The enzyme that absorbs a photon of light for photoactivation repair is called __________.
The enzyme that absorbs a photon of light for photoactivation repair is called __________.
Match the DNA repair steps with their correct descriptions:
Match the DNA repair steps with their correct descriptions:
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Study Notes
DNA Repair Mechanisms
- DNA is a stable molecule but can be damaged by environmental factors or replication errors.
- Damaged DNA can be quickly repaired, but if not, it becomes a mutation.
- Mutations in germline cells are inheritable.
Importance of DNA Repair
- Mutations can lead to cancer, genetic diseases, or even death.
- DNA repair mechanisms are essential for maintaining genetic integrity and preventing disease.
Photoreactivation Repair
- This repair mechanism is found in prokaryotes and eukaryotes.
- It directly reverses the formation of thymine dimers caused by UV radiation.
- The enzyme photolyase uses blue light to cleave the bond forming the dimer.
Excision Repair
- This is a three-step process involving recognition, removal, and replacement of damaged DNA.
- Base excision repair (BER) corrects damage to nitrogenous bases caused by spontaneous hydrolysis or chemical alteration.
- Nucleotide excision repair (NER) removes bulky lesions that distort the DNA double helix.
- Both involve enzymes like nucleases, DNA polymerase I, and DNA ligase.
Mismatch Repair (MMR)
- DNA polymerases have proofreading capabilities but some errors may escape during replication.
- Mismatch repair enzymes correct these errors, preventing mutations.
- Failure to repair mismatches can lead to mutations with varying consequences.
Post-Replication Repair
- This repair mechanism is activated when damaged DNA escapes prior repair and disrupts replication.
- The RecA protein promotes recombination between the damaged strand and a donor strand.
- This creates a gap in the donor strand which is then repaired by DNA polymerase and ligase.
DNA Repair Deficiencies and Diseases
- Xeroderma pigmentosum (XP): Caused by defects in DNA repair pathways, particularly those involved in repairing UV-damaged DNA.
- Ataxia telangiectasia (AT): Associated with sensitivity to gamma irradiation and defects in DNA repair pathways.
- Fanconi’s anemia: Results from a deficiency in repairing DNA cross-links.
- Lynch Syndrome (LS): Inherited cancer predisposition syndrome caused by mutations in mismatch repair genes.
- LS is associated with a higher risk of developing various cancers, including colorectal, endometrial, gastric, and ovarian cancers.
Lynch Syndrome (LS)
- LS is autosomal dominant with variable expressivity, meaning affected family members may have different signs and symptoms.
- Mutations in MMR genes (MLH1, MSH2, MSH6, PMS2, or EPCAM) are responsible for LS.
- Defects in MMR lead to an accumulation of mutations, increasing the risk of cancer.
Importance of DNA Repair Research
- Understanding DNA repair pathways is crucial for developing therapies targeting cancer and other diseases caused by genetic damage.
- Further research is necessary to identify new targets for therapeutic interventions and improve existing treatment strategies.
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