Mutations Flashcards
What is a mutation?
A heritable change to the DNA sequence of an organism
What is a wild-type allele?
The most prevalent allele in a population
What are 4 ways to classify mutations?
Where it came from, effects at a molecular level, effects on the phenotype, effects on gene product activity
Can mutations be spontaneous?
Yes, but they are rare because of proofreading mechanisms and repair find and fix most of them
What is a mutagen?
A substance that induces a mutation
What are the 3 classes of mutagens?
Chemical, physical, biological
What type of mutations are generated by chemical mutagens?
Point mutations
What are the 3 major mechanisms used by chemical mutagens to generate mutations?
Base modification, intercalating into the DNA backbone, base analogs
How does base modification create mutations?
Adding modifications to bases changes their H bonding properties, so they base pair with something else
What mechanism does EMS cause mutations through?
Base modification. Changes guanine to O-6-ethylguanine which base pairs with a T instead of C. Causes base pair substitutions
How does backbone intercalation create mutations?
Alters the physical structure of DNA and stalls replication, leading to the incorporation of incorrect bases
What mechanism do acridine and ethidium bromide cause mutations through?
Backbone intercalation. They are large, planar, multi-ringed molecules that in between the bases and disrupt the structure of DNA. Cause indels
How do base analogs create mutations?
They mimic normal bases and get incorporated during replication, but they base pair with the wrong thing
What mechanism does 5-bromouracil cause mutations through?
It mimics a thymine, so gets incorporated during DNA replication. The enol form will base pair with a G instead of an A
What types of mutations are generated by physical mutagens?
Large scale double strand breaks that result in deletions, inversions, or translocations. Pyrimidine dimers