47 Questions
Which process refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules?
DNA repair
What is the rate of DNA damage occurrence per cell per day due to environmental factors and normal metabolic processes?
1,000 to 1,000,000 lesions
What happens if DNA damage is unrepairable?
Cell cycle arrest
What does a failure to repair DNA produce?
Mutation
Which type of DNA damage is caused by the formation of pyrimidine dimers due to UV radiation?
Pyrimidine dimers
What is the primary effect of deamination in DNA?
Formation of uracil
Which repair mechanism involves the removal and replacement of damaged bases by specialized sets of enzymes including Nucleotide Excision Repair (NER)?
Excision repair
What is the main function of glycosylase enzymes in Base Excision Repair (BER)?
Replacing damaged bases from their sugar linkage
Which repair mechanism is the most frequent cause of point mutations in humans?
Direct reversal
Which enzyme is responsible for recognizing uracil and cutting the glycosyl linkage to deoxyribose?
Uracil glycosylase
What type of mutations are observed in mutants lacking uracil glycosylase?
Elevated spontaneous mutation levels
Which process removes whole oligonucleotides containing damage and repairs 'bulky' lesions in DNA?
Nucleotide excision repair (NER)
What type of damage is caused by UV radiation?
Thymine-thymine dimer residues
Which proteins are involved in removing damaged nucleotides in E. coli?
UvrA, UvrB, and UvrC
Which repair pathway responds when damaged DNA disrupts replication?
Post-replication repair
What decreases the error rate in DNA replication by two orders of magnitude?
Proofreading
'Double-stranded breaks are dangerous' - What are the two pathways involved in repairing them?
Non-homologous end joining and nucleotide excision repair
Which autosomal recessive disease is associated with sun sensitivity, freckling, and skin tumors?
Xeroderma pigmentosum (XP)
How many complementation groups have been identified for Fanconi anemia (FA)?
Seven complementation groups
Which FA gene has a role in DNA repair but its function is still unclear?
BRCA2
What is the main consequence of unrepaired DNA damage?
Genomic instability leading to mutations and cancer
What is the average rate of molecular lesions per cell per day due to DNA damage?
1,000 to 10,000 lesions
What is the function of DNA repair enzymes?
To identify and correct DNA damage
What is the role of p53 in response to unrepairable DNA damage?
Induces cell cycle arrest
Which type of DNA damage is caused by the formation of pyrimidine dimers due to UV radiation?
Pyrimidine dimers
What are the primary functions of glycosylase enzymes in Base Excision Repair (BER)?
Removing damaged bases and filling the gap with new nucleotides
Which repair mechanism involves the removal and replacement of damaged bases by specialized sets of enzymes?
Excision repair
What is the most frequent cause of point mutations in humans and is repaired by enzymes like glycosylases?
Direct reversal
Which repair mechanism responds when damaged DNA disrupts replication?
BER
What decreases the error rate in DNA replication by two orders of magnitude?
Proofreading by DNA polymerase
Which type of repair mechanism involves the rejoining of broken DNA strands?
Double-stranded break repair
'Humans lack the photoreactivation mechanism for repairing pyrimidine dimers.' What is the alternative repair mechanism for pyrimidine dimers in humans?
BER
'Endogenous damage is caused by cellular processes, while exogenous damage comes from external sources.' What are examples of exogenous sources of DNA damage?
UV radiation, other radiation, and chemicals
What is the primary effect of deamination in DNA?
Formation of uracil
What is the rate of DNA damage occurrence per cell per day due to environmental factors and normal metabolic processes?
100,000 occurrences per cell per day
Which autosomal recessive disease is associated with sun sensitivity, freckling, and skin tumors?
Xeroderma pigmentosum (XP)
What is the primary function of uracil glycosylase in DNA repair?
Removing and replacing damaged uracil bases
Which repair mechanism involves the removal and replacement of damaged bases by specialized sets of enzymes, including Nucleotide Excision Repair (NER)?
Nucleotide Excision Repair (NER)
What type of DNA damage is caused by the formation of pyrimidine dimers due to UV radiation?
Thymine-thymine dimer residues
Which process removes whole oligonucleotides containing damage and repairs 'bulky' lesions in DNA?
Nucleotide Excision Repair (NER)
What type of mutations are observed in mutants lacking uracil glycosylase?
Point mutations
'Double-stranded breaks are dangerous' - What are the two pathways involved in repairing them?
Non-homologous end joining and Nucleotide Excision Repair
What decreases the error rate in DNA replication by two orders of magnitude?
Proofreading
'Double-stranded breaks are dangerous' - What happens if non-homologous end joining glues the broken ends back together?
Point mutations are produced
'Non-homologous end joining glues the broken ends back together, producing mutations.' - What happens if homologous recombination repairs double-stranded breaks?
Mutation is prevented
'What is the rate of DNA damage occurrence per cell per day due to environmental factors and normal metabolic processes?' - Which of the following represents the approximate rate?
$10^7$- $10^8$ occurrences/cell/day
Which autosomal recessive disease is characterized by progressive bone marrow failure and hypersensitivity to DNA cross-linking agents?
Fanconi anemia (FA)
Study Notes
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Uracil is recognized by an enzyme that cuts the glycosyl linkage to deoxyribose, leading to the removal of the damaged sugar and the insertion of a new base by DNA polymerase using the other strand as a template.
-
Mutants lacking uracil glycosylase have elevated spontaneous mutation levels.
-
Nucleotide excision repair (NER) removes whole oligonucleotides containing damage, repairing "bulky" lesions in DNA and maintaining the regular DNA double helix.
-
Thymine-thymine dimer residues are examples of damage caused by UV radiation.
-
In E. coli, the UvrA, UvrB, and UvrC proteins are involved in removing damaged nucleotides.
-
UvrA recognizes the damage and recruits UvrB and UvrC, which cleave at the 3' and 5' sites of the damage, respectively.
-
DNA polymerase fills the gap, and ligase seals the repaired strand.
-
NER is also present in eukaryotes, with proteins having similar functions.
-
Proofreading decreases the error rate in DNA replication by two orders of magnitude, while mismatch repair corrects mismatches in the DNA strand.
-
In bacteria, mismatch repair is based on the process of DNA Methylation.
-
Double-stranded breaks are dangerous, and two pathways, non-homologous end joining and homologous recombination, are involved in repairing them.
-
Non-homologous end joining glues the broken ends back together, producing mutations.
-
Post-replication repair responds when damaged DNA disrupts replication.
-
Xeroderma pigmentosum (XP) is an autosomal recessive disease associated with sun sensitivity, freckling, and skin tumors.
-
XP patients have defects in genes homologous to those required for NER in simple eukaryotes.
-
Fanconi anemia (FA) is an autosomal recessive disease characterized by progressive bone marrow failure and hypersensitivity to DNA cross-linking agents.
-
Seven complementation groups (FANCA-G) are identified, with the most prevalent group A (FANCA) mutations accounting for 70% of cases.
-
At least seven FA genes have been identified: A, C, D2, E, F, G, and BRCA2.
-
The FANC genes have roles in DNA repair, but their functions are still unclear.
-
Uracil is recognized by an enzyme that cuts the glycosyl linkage to deoxyribose, leading to the removal of the damaged sugar and the insertion of a new base by DNA polymerase using the other strand as a template.
-
Mutants lacking uracil glycosylase have elevated spontaneous mutation levels.
-
Nucleotide excision repair (NER) removes whole oligonucleotides containing damage, repairing "bulky" lesions in DNA and maintaining the regular DNA double helix.
-
Thymine-thymine dimer residues are examples of damage caused by UV radiation.
-
In E. coli, the UvrA, UvrB, and UvrC proteins are involved in removing damaged nucleotides.
-
UvrA recognizes the damage and recruits UvrB and UvrC, which cleave at the 3' and 5' sites of the damage, respectively.
-
DNA polymerase fills the gap, and ligase seals the repaired strand.
-
NER is also present in eukaryotes, with proteins having similar functions.
-
Proofreading decreases the error rate in DNA replication by two orders of magnitude, while mismatch repair corrects mismatches in the DNA strand.
-
In bacteria, mismatch repair is based on the process of DNA Methylation.
-
Double-stranded breaks are dangerous, and two pathways, non-homologous end joining and homologous recombination, are involved in repairing them.
-
Non-homologous end joining glues the broken ends back together, producing mutations.
-
Post-replication repair responds when damaged DNA disrupts replication.
-
Xeroderma pigmentosum (XP) is an autosomal recessive disease associated with sun sensitivity, freckling, and skin tumors.
-
XP patients have defects in genes homologous to those required for NER in simple eukaryotes.
-
Fanconi anemia (FA) is an autosomal recessive disease characterized by progressive bone marrow failure and hypersensitivity to DNA cross-linking agents.
-
Seven complementation groups (FANCA-G) are identified, with the most prevalent group A (FANCA) mutations accounting for 70% of cases.
-
At least seven FA genes have been identified: A, C, D2, E, F, G, and BRCA2.
-
The FANC genes have roles in DNA repair, but their functions are still unclear.
This quiz covers the topic of DNA damage and repair in medical biology, focusing on the consequences of DNA damage and the mechanisms of repair. It discusses how changes in DNA structure can lead to mutations and the impact of environmental factors on DNA damage.
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