DNA Mutation and Repair
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Created by:
braidedtortoise on May 16, 2010
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33 terms
Terms | Definitions |
|---|---|
 Silent Mutation | Base substitution that does not change the codon. |
| Missense Mutation | Base substitution that does change the codon. |
| Nonsense Mutation | Base substitution that codes for a STOP codon too early. |
| Frameshift Mutation | Base addition or deletion that affects all following codons. |
| Nucleotide substitution | one base pair is replaced with a different base pair |
| Transition | pyrimidine (C/T) to pyrimidine or purine (G/A) to purine |
| Transversion | pyrimidine to purine / purine to pyrimidine |
| Insertion | one or more extra nucleotides present |
| Deletion | one or more nucleotides absent |
| Spontaneous Mutation | occurs in absence of known mutagen |
| Induced Mutation | occurs in presence of known mutagen |
| Germ line Mutation | in reproductive cells |
| Somatic Mutation | in nonreproductive cells |
| Conditional Mutation | expressed in restrictive but not permissive conditions |
| Loss-of-function Mutation | eliminates normal function |
| Hypomorphic Mutation | reduces normal function |
| Hypermorphic Mutation | increases normal function |
| Gain-of-function Mutation | expressed at wrong time or in incorrect location |
| Depurination | Removal of an adenine or guanine, Deoxyribose and purine base have a relatively unstable covalent interaction, Mammalian cell looses 10,000 purines every 20 hours |
| Tautomeric Shift | TEMPERARY Essentially the shifting of electrons Guanine and thymine: keto to an enol/ Adenine and cytosine: amino to imino |
| Deamination | Deamination of cytosine leads to uracil. Uracil is not a normal component of DNA and can be recognized and removed. Deamination of 5-methylcytosine leads to thymine. Thymine is a normal component of DNA and is not recognized as a source of potential mutation. |
| Base Alkylation | Alkyl group covalently attached (CH3) |
| Intercalating agents | acridine orange, proflavin, ethidium bromide (used in labs as dyes and mutagens) Flat multiple ring molecules Interact with bases of DNA and insert between them Insertion causes a "stretching" of the DNA duplex DNA polymerase is "fooled" into inserting an extra base opposite an intercalated molecule intercalating agents cause frameshifts. |
| Thymidine Dimer | Two adjacent pyrimidine bases, typically a pair of thymines, in the polynucleotide strand, between which chemical bonds have formed; the most common lesion formed in DNA by exposure to ultraviolet light. |
| Ames Test | A bacterial test for a mutagenicity; also used to screen for potential carcinogens. Used Rat live enzyme, the unknown chemical, and a histidine auxotroph type of salmonella. |
| Dynamic Mutation | Term applies to certain sequences composed of tandem repeats that show genetic instability owing to a relatively high frequency of change in the number of copies of the repeat from one generation to the next. |
| Direct Repair | Reversal of covalent modifications/ Repair thymidine dimers (use enzyme, photolyase) |
| Base Excision Repair | A mechanism of DNA repair initiated by removal of a mismatched or damaged base from its associated deoxyribonucleotide sugar. Recognize: uracil (NOT IN DNA) 3 methyladenine 7 methlyguanine pyrimidine dimers OG (from oxidation of G) |
| Nucleotide Excision Repair | A mechanism of DNA repair in which nucleotides with mismatched or damaged bases are cleaved from a DNA strand and replaced using the complementary DNA strand as a template.UvrA and B scans for irregularities UvrB,C nick region surrounding dimer UvrD helicase unwinds region, releases strand DNA pol fills in gap Ligase seals repaired strand |
| Mismatch Repair (methyl directed) | Removal of one nucleotide from a pair that cannot properly hydrogen-bond, followed by replacement with a nucleotide that can hydrogen-bond. |
| Recombinatorial Repair | Repair of damaged DNA by exchange of good for bad segments between two damaged molecules. |
| Translesion DNA Polymerases | Special active site with large pocket that allows for polymerase to go over the error, more likely to incorporate incorrect nucleotides |
| E. coli SOS response | An inducible, error-prone system for repair of DNA damage in E. coli. Enzymes are attracted to stalled replication forks. |
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