Lecture 23

Question 1

In what ways can mutagens induce mutations

Answer 1

They can alter a base so it pairs with another (like deamination)
Can alter/damage a base to the point of stalling DNA replication machinery
Damage to a base such that it cant pair with anything (like UV and thymine dimer)
A base can be replaced by a chemical analog (a chemical with similar structure)
Most of these cause point mutations

Question 2

Intercalating agents

Answer 2

Mutagens that can cause small insertions or deletions
They have a similar structure to DNA nucleotides so they can kind of wiggle their way in and “act” like a nucleotide
Still technically considered a point mutation due to the scale but technically its an insertion/deletion

Question 3

Ames test

Answer 3

Test used to determine whether a compound is a mutagen
His-mutant strain of salmonella bacteria (not capable of making histidine) is exposed to the mutagen in a low-histidine medium and you see whether or not colonies grow, if they do grow in a low histidine medium it means theyre no longer auxotrophic for that amino acid therefore the underwent a mutation to fix it, so mutation rate must be high with that compound

Question 4

What’s a disadvantage of the Ames test

Answer 4

Salmonella bacteria are not multicellular organisms, so not entirely representative, especially since multicellular organism process stuff, break it down and then you get a whole new possibly mutagenic compound
Also if you have a frameshift it’ll be much harder to revert such a mutation rather than point mutation, so if your strain happens to be a frame shift strain you’ll likely see few colonies when ut actually has caused a lot of mutations

Question 5

Revised Ames test

Answer 5

Has the same components as before with an addition, liver enzymes to simulate the processing we would give this compound