Lecture 12 - Mutagens & the AMES Test Flashcards
What are physical mutagens?
- Ionizing radiation: cosmic rays, X-rays and gamma rays (radioactive decay)
- Ultraviolet radiation from sunlight
What are chemical mutagens?
- Base analogs
- Base modifying agents
- Intercalating agents
What does ionizing radiation result in?
Change stable molecule to a free radical or reactive ions, which can alter the structure of bases and break phosphodiester bonds in DNA
What are base analogs and what do they cause?
chemicals that appear similar to the normal bases in DNA, but causes incorrect base-pairing and introduce point mutations during DNA replication
What are base modifying agents and what do they cause?
chemicals that modify groups on the normal bases in DNA that result in incorrect bare-pairing during DNA replication
What are intercalating agents and what do they cause?
chemicals that distort the normal stacking of bases in DNA resulting in insertion or deletion of a single base-pair during DNA replication
What does the nucleotide analog 5-bromouracil look similar to?
both thymine and cytosine
When does the mutagenic effect of 5-bromouracil occur?
During DNA replication
What does an intercalating agent do what does it result in?
distorts the adjacent bases in the DNA by 0.68 nm (the width of a base), results in frame-shift mutation owing to insertion of one base pair
What is the AMES test?
a simple method to measure the reversion of a mutant His- Salmonella bacterial strain to His+ Salmonella wild-type strain by potential mutagens
What can His- Salmonella not grow on that His+ Salmonella can grow on?
minimal medium lacking the essential amino acid, histidine
What does increased reversions of His- to His+ Salmonella indicate?
that the chemical is a mutagen, and thus a potential carcinogen
