Term
| Prokaryotic nucleotide excision repair enzymes and use? |
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Definition
Uses UVr ABCD system;
A - Locates
B - Cuts 3' end
C - Cuts 5' end
D - removes (it's helicase III)
-used to repair many things other than mismatches |
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Term
| Eukaryotic Nucleotide Excision Repair (NER) enzymes, diseases, and what causes damage corrected by NER? |
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Definition
-Proteins from XP-genes (A thru G) do NER in humans
-Xeroderma Pigmentosa (XP) - can't excise DNA
-Cockayne Syndrome - Bad ERCC 6 or 8
-Trichothiodystrophy - Bad XPB,D, or G
-UV light and chemicals |
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Term
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Definition
| Carcinogen in cigarette smoke that binds to guanine and interferes with GC pairing. |
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Term
| Xeroderma Pigmentosum (XP) |
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Definition
-UV induced lesions with terrible blistering and freckling where exposed to sun
-usually die of skin cancer in teens
-caused by error in NER where the DNA can't be excised where there is UV induced bulky lesion (such as T dimers) |
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Term
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Definition
-Bad Excision Repair Cross Complimenting (ERCC) proteins which are part of NER
-ERCC 6 or 8 (type B and A respectively) involved with repair during TRANSCRIPTION
-Causes PREMATURE AGING, dwarfism, mental retardation, and neurological degeneration
-Compared to XP, we get PHOTOSENSITIVITY, but much less, and no increased risk of cancer |
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Term
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Definition
- Bad XP B,D, or G (in NER)
- Causes brittle hair, short stature, scaly skin, and mental retardation |
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Term
| Prokaryotic mismatch repair enzymes? Directed by? |
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Definition
Uses Mut H/L/S repair system
-Mut H - endonuclease, binds to hemimethylated GACT site
-Mut L - binds H & S together
-Mut S - finds damage and recruits ENDONUCLEASE I (damage towards 3' from GACT) or ENDONUCLEASE VII (towards 5')
ssBPs then protect the strand till DNA Pol III and ligase step in to do the patch work
-Directed by DNA Adenine Methylation (DAM) at GACT sequence. Heavier methylation indicates "parent strand" |
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Term
| Eukaryotic mismatch repair enzymes, diseases, and what causes damage corrected by mismatch repair? |
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Definition
-Uses hMLH1 & 2 in humans
-Does not use methylation to distinguish parent from daughter strand. Instead enzymes look for nicks in new DNA.
-Disease is HNPCC/Lynch Syndrome
-Damage from DNA replication errors |
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Term
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Definition
-Stands for Hereditary Nonpolyposis Corectal Cancer (AKA lynch syndrome)
-Caused by mutation in hMSH1 or 2 genes
-Results in high risk for CORECTAL CANCER, often with absence of polyps, and typically on the RIGHT SIDE (average onset is at age 42)
-The best diagnostic evidence is microsatellite instability |
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Term
| Eukaryotic Base Excision Repair (BER) enzymes, what is repaired, diseases, and what causes damage corrected by BER? |
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Definition
-DNA Glycosylase (such as uracil gylcosylase)-removes BASE (not needed in depurination damage)
-AP endonuclease - cleaves
-Then DNA Pol & Ligase combo
-used for repair of deaminations (C to U or A to HX), depurinations, and alkylated bases
-BER diseases are Hyper IgM Syndrome (lack UNG2), and increased risk of lung cancer (mutated OGG1)
-Damage may be caused by free radicals, alkylating agents, and hydrolysis |
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Term
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Definition
-deficient UNG2 - a uracil glycosylase in B-Cells (a BER enzyme)
-it is used to purposely cause mutations to get more variation in produced antibodies
-Causes immunodeficiency with recurrent infections |
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Term
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Definition
-OGG1 is a DNA glycosylase (BER enzyme) that removes oxidized bases such as 8-oxoguanine
-deficiency causes increased risk of lung cancer |
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Term
| Double Stranded DNA Break Repair pathways, diseases, and things that can cause the damage? |
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Definition
HOMOLOGOUS RECOMBINATION (HR)
-requires a template and functions in all but G1/0 when there is a template around to base the repair off of
-Deficiency of pathway results in Bloom Syndrome and Breast Cancer Susceptibility 1 & 2 (BRCA 1 & 2)
NONHOMOLOGOUS END-JOINING (NHEJ)
-Doesn't use template, so is more susceptible to errors
-When def. we get SCID and Radiation Sensitive SCID
-Damage can be from ionizing radiation, X-rays, and anti-tumor drugs |
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Term
| Bloom Syndrome, enzyme, gene, and chromosome? Characteristics? Symptoms? |
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Definition
-caused by DNA ReqQ Helicase encoded by Bloom gene on chromosome 15 (a DNA break repair enzyme)
-DNA replication AND repair are impaired
-Get extra sister exchange and DNA fragility
-Causes light sensitivity with BUTTERFLY-SHAPED PATCHES, and SPIDERY BLOOD VESSELS
-Also results in developmental delay presenting as long narrow face, low set ears, and small jaw
-Increased risk of cancer |
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Term
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Definition
-Decreased ability to repair interstrand DNA cross-links
-Susceptible to DNA damaging agents
-Prone to early cancer
-Have BONE MARROW INSUFFICIENCY with leukopenia (low WBC)
-Also presents with microcephaly and mental retardation |
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Term
| Direct Repair in prokaryotes? |
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Definition
-Uses PHOTOLYASE which has a light dependent repair mech.
-Often for fixing T-T dimers. |
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Term
| Direct Repair in eukaryotes, enzyme, what does it repair, and what is the mechanism? |
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Definition
-Uses DNA Alkyltransferases to remove alkyl groups from O6-methylguanine and O6-ethylguanine
-These were formed spontaneously, or because of chemicals, smoke, etc.
-The mechanism uses a CYSTEINE residue in the active site to accept the alkyl group (thereby inactivating the enzyme) |
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Term
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Definition
-Used to test if compounds are carcinogenic
-Uses an altered Salmonella typhimurium with a His- mutation (rather than wild type His+)
-Works because carcinogen exposure will result in an increased instance of its reversion to wild type, and thus ability to grow in the absence of His |
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