Term
| Differences between Eukaryotic and Prokaryotic DNA replication |
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Definition
Prokaryotes: Curcular chromosomes, One origin of replication
Eukaryotes: Linear Chromosomes, many origins of replication |
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Term
| Differences in Properties of DNA and RNA polymerases |
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Definition
DNA Polymerase: Proofreading activity, highly accurate, very processive, require a primer
RNA Polymerase: No proofreading, error prone, not very processive, no primer needed (have PPP at 5') |
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Term
| Features of the Replication Fork: Gyrase |
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Definition
| Introduces negative supercoils ahead of replicating fork |
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Term
| Features of the Replication Fork: Helicase (dnaB) |
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Definition
| unwinds parent strands, relieving negative supercoils |
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Term
| Features of the Replication Fork: Leading Strand |
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Definition
-5' to 3' in direction of unwinding
-DNA Pol III: reads parent strand and inserts complimentary
-DNA polymerase: catalyzes formation of phosphodiester bond b/w original 3' and new 5' |
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Term
| Features of the Replication Fork: Lagging Strand |
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Definition
-Small DNA fragements (Okazaki) grow form small RNAs that serve as temporary primers
-Primase (dnaG in e. coli) makes RNA primers; provides 3' hydroxyl allowing DNA Pol III to make DNA
-RNaseH (DNA Pol I in Prokaryotes) excises short segments
-DNA Polymerase fills gaps
-DNA Ligase seals junction b/w DNA strands |
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Term
| Relationship between Mutations and DNA replicatoin |
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Definition
| Mutations are inherited changes in DNA and, thus, require DNA synthesis |
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Term
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Definition
| Change in a single DNA basepair |
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Term
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Definition
| Purine replaces by another purine (or Pyr for Pyr) in the same DNA strand |
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Term
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Definition
| Purine replaces by Pyrimidine (or vice versa) |
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Term
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Definition
| Transfer of segment of DNA from one position (or DNA strand) to another |
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Term
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Definition
| Addition of one or more nucleotide basepairs (can be cause by translocation) |
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Term
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Definition
| Removal of one or more basepairs |
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Term
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Definition
| Removal and reinsertion of seqeunces in opposite orientation |
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Term
| Spontaneous Mutation: Tautomeric Shift |
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Definition
| Rare electronic shift in DNA bases making one nucleotide mimic another |
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Term
| Radiation Mutation: Ionizing Radiation |
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Definition
| Displaces electrons in DNA bases; can sever phosphodiester bond |
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Term
| Radiation Mutation: UV Light |
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Definition
| Photoactivates pyrimidines, especially Thymine, causing thymine dimers; cross links Thy so polymerase doesn't recognize it |
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Term
| Chemical Mutation: Base Analogs |
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Definition
substitute for normal DNA bases but pair with different bases
Ex) Bromouracil replaces thymine but pairs with G, not A |
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Term
| Chemical Mutation: Alkylating Agents |
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Definition
| React with amino groups in bases |
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Term
| Chemical Mutation: Deaminating Agents |
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Definition
Remove amino groups
Ex) changing cytosine to uracil |
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Term
| Chemical Mutation: Intercalating Agents |
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Definition
Planar phenolic or multiple ring structures that insert b/w adjacent basepairs in DNA
Cause temporary frame shifts |
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Term
| Mutation Outcomes: Silent, Nonsense, Framshift, Missense |
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Definition
Silent: do not change amino acid sequence of encoded protein, no effect on phenotype
Nonsense: inserts premature stop codon
Frameshift: insertion or deletion altering reading frame
Missense: changes one codon to a different amino acid |
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Term
| DNA polymerase 3 proofreading activities: DNA polymerization, 3'-5' exonuclease, 5'-3' exonuclease |
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Definition
DNA polymerization: 5'-3' direction
3'-5' exonuclease: Causes DNA polymerase to back up, remove unmatched base, and reinsert correct nucleotide
5'-3' exonuclease: Removes RNA primer from DNA; removes damaged DNA |
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Term
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Definition
Repair complex binds to damaged site and unsecures DNA strand (~30 base pairs long). Excises this area from damaged strand.
DNA polymerase fills in gap
DNA Ligase joins loose ends |
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Term
| Apurinic Site/Cytidine Deamination Site Repair |
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Definition
Apurinic: Purine is removed (G, for example) from strand, AP endonuclease and DNA Polymerase Beta repair strand and replace the removed Purine (with G in this case), then DNA ligase secures the strand
Cytidine Deamination:Cytidine is deaminated and converted to Uracil, Uracil is removed by DNA glycosylase, AP endonuclease and DNA polymerase Beta repair strand and replace Cytidine, DNA ligase secures strand |
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Term
| Prominent Error of DNA repair enzyme (clinical correlate) |
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Definition
Xeroderma Pigmentosum is malfunction of nucleotide excision repair
Extreme sensitivity to light |
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Term
| What are telomeres and telomerase, and which cells maintain active telomerase? |
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Definition
Telomeres: ~250-1500 5'-TTAGGG-3' repeats at end of eukaryotic chromosomes
Telomerase: reverse transcriptase (requires RNA and Protein components); w/o telomerase, telomeres grow shorter w/ each chromosome replication (replicative cell senescence)
Stem, germ, and cancer cell maintain active telomerase |
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