Mutation Repair

Question 1

Mismatch Repair Can Fix

Answer 1

Incorrect Base Pair

Question 2

Nucleotide Excision Repair Can Fix

Answer 2

Altered Base, deletion or insertion, linked pyrimidines (UV radiation), cross-linked strands (STRUCTURAL DISTORTIONS)

Question 3

Homologous Recombination Can Fix

Answer 3

single or double stranded breaks caused by ionization or chemotherapy

Question 4

Nonhomologous End Joining Can Fix

Answer 4

single or double stranded breaks caused by ionization or chemotherapy

Question 5

Translesion DNA synthesis Can Fix

Answer 5

cross-linked strands, linked pyrimidines

Question 6

Mutation

Answer 6

heritable change in the sequence of DNA (change in genotype) - Watson crick pair changed to another normal W-C pair, not recognized as a mistake

Question 7

Damage

Answer 7

altered pairing (not W-C pair) that can still be recognized as a mistake (can turn into a mutation if not recognized)

Question 8

Mismatch Repair Mechanism

Answer 8

Corrects incorrect base pairings 1. MutH recognizes daughter strand (non-methylated) in prokaryotes (time sensitve) 2. MutS finds the mismatch 3. MutL binds S and H together 4. Mut H nicks daughter strand 5. helicase, exonuclease, DNA Pol and ligase do their jobs to resynthesize area

Question 9

Direct-Acting Mutagens

Answer 9

covalently modify DNA bases

Question 10

Indirect-Acting Mutagens

Answer 10

are water soluble and inert until activated by liver cytochrome P-450

Question 11

Nucleotide Excision Repair Mechanism

Answer 11

repairs environmentally-induced DNA damage, not time sensitive (can happen anytime) 1. distortion recognized in DNA by a protein dimer 2. Helicase and Stabilizers are recruited 3. incisions are made at 3’ and 5’ sides of distortion 4. Dna pol fills gap and ligase seals it

Question 12

Homologous Recombination Mechanism

Answer 12

repairs double stranded breaks (most lethal), this repair mechanism is the accurate way to join breaks (no lost info), uses strand invasion of homologous DNA strand from sister chromatid to resynthesize chromosomal DNA (MUST happen in S or G2 phases of cell cylce)

Question 13

Holliday Junctions

Answer 13

crossover points in homologous recombination between sister chromatids

Question 14

Nonhomologous End Joining Mechanism

Answer 14

error-prone rescue replication of double stranded breaks, predominant pathway, no specificity, CAUSES PROBLEMS! 1. DNA is unwound until a complementary sequence is found between the two broken double helices 2. once that is found they are joined together

Question 15

Reciprocal Translocation

Answer 15

problem with nonhomologous end-joining where ends of two different chromosome are switched with each other

Question 16

Inversion

Answer 16

problem with nonhomologous end-joining where the center of a chromosome is rejoined backwards from original orientation

Question 17

Translesion DNA synthesis Mechanism

Answer 17

if DNA polymerases encounters conformational change because of damage it will dissociate and TLS DNA pol will take over. TLS DNA pol has reduced fidelity and can accomodate altered pairings and continue synthesis. error prone and low processivity - will dissociate after a few bases and DNA pol will take back over

Question 18

Ames Test

Answer 18

test for mutagenic capabilities of compounds

Question 19

How does the Ames Test work?

Answer 19

use a His- bacteria (cannot replicate) and put mutagen in to see if any collonies grow (would have to be mutated). Can also add liver extract to see if mutagen is indirect or direct (will grow if indirect w/ liver extract)

Question 20

What are limitations of the Ames Test?

Answer 20

Only detects mutations to the His gene, says whethere a compound is mutagenic, not carcinogenic