mutations mod32 Flashcards
What are tautomer shifts
when the protons shift forming a rare form so a base analog
What is the rare imino base pairing
A:C
what is the rare enol base pairing
G:T
what is the effect of mismatched base pairs for rare imino
A:C base pairing results in C:G base pair sub
What is the effect of mismatched base pairs for rare enol
G:T base pairing results in T:A base pair
what factors influence the rate of spontaneous mutations
accuracy of the dna replication
efficiency of dna repair
what are the 2 types of chemical mutagens
Mutagenic to only replicating dna and mutagenic to both replicating and nonreplicating
what are the chemicals that are mutagenic only to replicating DNA
Base analogs and Acridines
what are the chemicals that are mutagenic to both replicating and non
Alkylating agents, deaminating agents and hydroxylating agents
Name the 2 base analogs
5 bromouracil BU
2 Aminopurine AP
name the acridine
Proflavin
Name a deaminating agent
Nitrous Acid
Name the hydroxylating agent
Hydroxylamine
Base analogs increase the likelihood of what happening
Mispairing
5 bromouracil is an analog of what base
Thymine
structure of 5 bromouracil
Br at position 5 instead of CH3
Br increases frequency of what
Tautomeric shifts
what does the following forms of 5BU pair with
1) stable keto form
2) instable enol form
1) pairs A
2) pairs G
What is the mutagenic effect of 5BU
Transition
When 5BU is present in its less frequent enol form, what happens
Induces G:C –> A:T
When 5BU is present in its common keto form, what happens
A:T –> G:C
Acridine dyes like proflavin cause what
Frameshift mutations
Proflavin affects the double helix in what way and how?
increases rigidity and alters conformation because proflavin gets in between the base pairs in DNA
What do alkylating agents do
add alkyl groups to base CH3
What do deaminating agents do
Remove NH2 from bases
Hydroxylamine does what
hydroxylates the amino group of cytosine and leads to G:C –> A:T transitions
Hydroxylamine is useful in classifying what
transition mutations
For lung cancer, what genes are mutated
Several anti cancer genes and chromosomes
How do Xrays and UV light induce mutations
Xrays - through ionisation
UV - through excitation (non ionizing radiation)
X rays can specifically mutate how
Breaks chromosomes, cause deletions, duplication, inversions and translocations
The increased what of atoms present in DNA is responsible for most mutagenicity ( Radiation)
The increased reactivity of atoms present in DNA molecules is responsible for most of the mutagenicity
what are the products of DNA that has absorbed UV radiation
Pyrimidine hydrates and pyrimidine dimers
what is a pyrimidine hydrate
UV + H20 = extra OH on the base
What is pyrmidine dimer
Two pyrimidine joined together
hydrolysis of cytosine to a hydrate causes what
mispairing during replicaton
Thymine dimers do what
block DNA replication and activate error-prone DNA repair mechanisms
UV can be used beneficially how
used to sterilise surface by inducing formation of thymine dimers which block dna replication
