Term
| Describe initiation in eukaryotes |
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Definition
1) tRNAimet binds to P site which binds to 5' 7MG cap on the mRNA
2) initiation complex scans 5' to 3' until it finds start codon (AUG)
3) initiation factors released, large subunits released |
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Term
| What is the difference in elgonation between prok. and euk.? |
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Definition
- Eukaryotes have EF-1a-GTP instead of EF-Tu-GTP
- Eukaryotes have EF-2, instead of EF-G |
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Term
| How many release factors are involved in eukaryotic translation? |
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Definition
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Term
| What does it mean that the genetic code is degenerate? |
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Definition
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Term
| What does it mean that genetic code is degenerate? |
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Definition
| That 1 amino acid can be coded for by more than one codon (a.k.a. Crick's wobble hypothesis) |
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Term
| What are nonsense mutations? |
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Definition
| When a codon specifying an a.a is changed to a stop codon |
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Term
| How can you suppress a nonsense mutation? |
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Definition
| Mutations in the anticodon sequence which will incorporate an amino acid into a stop codon |
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Term
| What are the seven types of mutations? |
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Definition
transition
transversion
silent
neutral
missense
nonsense
frameshift |
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Term
| What is a transition mutation? |
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Definition
| Changes a purine to another purine, or a pyrimidine to another pyrimidine |
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Term
| What is a transversion mutation? |
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Definition
| Substitutes a purine to a pyrimidine, or vice versa |
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Term
| What is a silent mutation? |
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Definition
| DNA sequence is altered, but maintains the same amino acid, and has no effect on the phenotype or function |
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Term
| What is a neutral mutation? |
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Definition
Amino acid is altered, but protein function is maintained
- is a form of missense mutation |
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Term
| What is a missense mutation? |
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Definition
| New amino acid is produced, MAY change protein function, but doesn't always. |
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Term
| What is a nonsense mutation? |
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Definition
| DNA sequence is altered, so that a stop codon is produced |
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Term
| What is a frameshift mutation? |
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Definition
Insertion or deletion of a nulceotide(s)
- only by 1, 2, 4, 5 not 3 or 6, etc. |
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Term
| What is a tautomeric mutation? |
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Definition
Movement of Hydrogen atoms b/w the same base (keto vs enol) (amino vs imino)
- leads to replication errors due to incorrect base pairing |
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Term
| What tautomers are more rare? Keto and amino, or enol and imino? |
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Definition
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Term
| What do alkylating agents do? |
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Definition
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Term
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Definition
| Substitutes for a normal base |
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Term
| True or False: Analog bases cannot undergo tautomeric bases |
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Definition
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Term
| What does nitrous acid do? |
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Definition
| Modifies bases resulting in errors in base-pairing (oxidative deamination) |
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Term
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Definition
| They create frameshift mutations by inserting or deleting single nucleotides |
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Term
| What effect does UV light have on nucleotides? |
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Definition
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Term
| What effect do x-rays have on DNA? |
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Definition
| Break glycosidic bond b/w sugar and base creating apurinic or apyrimidinic sites (the removal of a purine or pyrimidine) |
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Term
| How can you screen for mutagenic compounds? |
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Definition
The Ames test
- measures the ability to convert His- mutants to His+ mutants (salmonella) |
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Term
| Does photo-reactivation occurs in prokaryotes or eukaryotes? |
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Definition
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Term
| How does photo-reactivation repair work? |
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Definition
| Uses light energy to activate DNA photolyase enzymes to repair thymine dimers |
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Term
| What enzymes are required for base-excision repair? |
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Definition
AP endonuclease
Glycosylase (removes base)
Phosphodiesterase (removes sugar-phosphate)
DNA Polymerase (inserts correct nucleotide)
Lygase (rejoins phosphodiester bonds) |
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Term
| Other than photo-reactivation repair, how can thymine dimers be repaired? |
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Definition
| Nucleotide excision repair - removes 12 base strand |
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Term
| What does nucleotide excision require? |
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Definition
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Term
| What is the difference in nucleotide excision repair b/w prok. and euk.? |
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Definition
| So... Eukaryotes remove larger streches of DNA, require XPA proteins |
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Term
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Definition
Corrects replication errors in E. coli
- recognizes the absence of a methylated A in the sequence GATC |
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Term
| What proteins are required for mismatch repair? |
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Definition
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Term
| What is the SOS response, and what proteins induce it? |
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Definition
| An error-prone repair response, induced by the LexA and RecA proteins |
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Term
| What is post-replication repair? |
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Definition
| Uses homologous recombination to fix gaps created when the replication fork skips over an unrepaired thymine dimer |
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Term
| What are the two forms of double-strand break repair? |
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Definition
1) homologous (requires Rad proteins)
2) non-homologous end-joining |
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Term
| True or False: Non-homologous end-joining conserves DNA |
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Definition
| False; cutting and trimming results in loss of some DNA |
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