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20 Cards in this Set

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Why are mutations important?
Basis of genetic analysis.
Needed to understand evolution.
Not always bad
What are spontaneous mutations?
Accidental.
Rate is low and differs between organisms and genes
from error of polymerase
What are induced mutations?
From natural or chemical/artificial agents.
Mutations in somatic cells aren't passed to next generation
What is conditional phenotypic expression?
Mutations whose expression occurs during certain conditions.
Mutation can create a normal protein if at a certain temp, but if temp changes, mutated form is expressed.
What is a point mutation?
Change one base for another.
Missense: wrong aa inserted
Nonsense: becomes stop codon
Silent: codon changed but not aa
What is a frameshift mutation?
New arrangement of codons, caused by insertion or deletion and the effects depend on placement of shift.
What is transition?
Pyrimidine replaces pyrimidine, etc
What is tranversion?
Purine replaces pyrimidine.
What are tautomeric shifts?
Bases differ by proton shift. Normally bind keto/amino
Enol thymine can base pair with keto guanine.
Imino cytosine can base pair with amino form of adenine
natural process, occurs spontaneously when free and can shift back to normal tautomer after another round of replicaton. Can become a point mutation after replictaiton.
Describe 5-bromouracil.
Base analog: mutagenic chemicals that can substitute for purines or pyrimides during nucleic acid synthesis. Look up in notes.
Discuss alkylating agents:
Add methyl/ketyl group to amino/keto groups of bases: same thing as base analogs
Discuss acridine dyes.
ethydium bromide causes insertion/deletion mutations becasue intercoloring agents fits between bases.
Discuss UV light and mutations.
Cannot be reversed back to original form.
Causes dimers to be made: covalent bonds between T residues.
Dimers cause DNA conformational changes, can be skipped during replication... causes mistakes to occur.
Ames test.
Tests for mutagens, NOT carcinogens.
Discuss DNA repair during replication.
DnA pol can go back and replace wrong bases.
How does it know which is the template vs. new strand?
Adenine methylase recognizes sequence GATC and adds methyl to adenine. New strand is temporarily unmethylated bc methylase lags behind polymerase.
Discuss excision repair.
Error clipped out by endonuclease
DNA pol I fills in gap
Ligase seals backbone
Discuss base excision repair.
corrects damage to bases from chemicals
Discuss nucelotide excision repai
corrects bulky lesions in DNA tha alter double helix
Double strand break repair.
Last resort. Enzyme recognizes double strand break. 5' end of break is digested. 3' end looks for complementary sequence and aligns with it.