MUTATION & MUTAGENESIS Flashcards
What about point mutations?
They are the most common and the least dangerous
Most dangerous mutations
Addition or deletion
What are pyrimidines?
C/T/U
What are purines?
A/G
3 main causes of mutations
1) DNA damage
2) random insertion of transposable elements
3) Replication errors
Describe a transition point mutation
The mutation of a pyrimidine to a pyrimidine or a purine to a purine
Describe a transversion point mutation
The mutation of a purine to a pyrimidine or pyrimidine to a purine
What is a tautomer?
What kind of mutation do they cause?
An alternative form of a nucleotide base that bonds to a different base from its usual complement
- Can cause a point mutation.
Thymine is normal in its __(a)__ form. Its tautomer is called the __(b)___ form and has a double bonded ___(c)___. This means that it binds to ___(d)____ as opposed to ___(e)____.
a) keto
b) enol
c) Nitrogen
d) guanine
e) adenine
Cytosine is normal in its ___(a)___ form. Its tautomer is called the ___(b)__ form and binds to ___(c)___ instead of ___(d)____.
a) amino
b) imino
c) adenine
d) guanine
3 ways in which errors in DNA replication can lead to mutation
1) failure of the epsilon subunit to correct mismatch when proof reading
2) tautomeric shift causing mismatches
3) replication slippage
a) How do replication slippages occur?
a) repeating bases such as ctctctct will bind to a corresponding sequence elsewhere creating a loop or slip
- DNA repair will often delete the loop and cause a frameshift
A slippage on the TEMPLATE strand can cause….
deletions
A slippage on the NEWLY SYNTHESISED STRAND can cause…
additions
EXTERNAL damage to DNA
a) How does UV radiation damage DNA?
b) How does ionising radiation damage DNA?
c) How do external chemicals such as cigarette smoke damage DNA?
a) cause pyrimidine dimers to be formed
b) breaks in DNA
c) can damage bases
