Topic 6 Flashcards
What is dna damage and how can it occur
Any modification of dna that changes its coding properties or normal function in transcription or translation
Can happen spontaneously, induced by exposure to environmental factors like chemicals or radiation, or during replication
What can dna damage lead to
Are most mutations harmful
Mutations and genetic instability
Yes
What can cause changes in genetic material
Gene mutation (can be spontaneous or induced by mutagens)
Recombination (causing chromosomal rearrangements)
Transposable elements
Give an example of how recombination can change genetic material
If the chromosomes aren’t aligned properly during recombination
In one strand a deletion of a fragment can happen and a duplication in the other
What can cause gene mutations
Replication errors
Chemical modifications
What are the mutations that are caused by replication errors
What is the result of replication errors
Point mutations
Frameshift mutations
Mismatching, deletion, insertion, causing the reading frame to be same or diff
What are point mutations
A change in a single nucleotide
Can cause missense (change in nucleotide made diff amino acid) or nonsense mutations (premature stop codon
What are frameshift mutations
The slippage of the dna pol on the template causes a deletion in the new strand
Slippage on the new strand causes an addition in the new strand
Guanine and adenine structure and numbering
Both two rings
Guanine has c=o at c6
Adenine has c-NH2 at c6
In the five c ring numbers 7,8,9
In the 6 c ring the c 6 then go clockwise backward
Cytosine, thymine, uracil structure and numbering
Single ring for all
Cytosine has c-NH2 on c 4
Thymine has c=o on c 4 and methyl on c 5
Uracil same and thymine but no methyl on c 5
Number from 1 opposite to c 4 going clockwise
Which atom of purine and pyrimidines form bind with the sugar
Purine: N9
Pyrimidine: N1
What is a tautomeric shift
The dominant keto (c=o) and amino (c-nh2)
Turn to enol (c-oh) and imino (c-nh
Which nucleotides can have enol forms
Which can have imino
Guanine thymine and uracil
Adenine cytosine
What can enol form of thymine base pair with
Say how it changes
Keto guanine
T:A then T:G
after replication C:G
What can enol form of guanine base pair with
Say how it changes
Keto thymine
G:C to G:T
After replication A:T
What can imino form of adenine base pair with
Say how it changes
Amino form of cytosine
A:T to A:C
After replication G:C
What can imino form of cytosine base pair with
Say how it changes
The amino form of adenine
C:G to C:A
After replication T:A
What is the result of anomalous base pairing due to tautomeric shifts
Base pair transitions or transversions
What is a transition mutation
Transversion
Purine pyrimidines to purine pyrimidines (ex. G:C turns to A:T)
Purine pyrimidines to pyrimidines purine (ex. G:C turns to C:G)
Point mutations can be categorized into
Translation or transversion mitations
What are the two steps that point mutations occur in
At what pint is it actually a mutation
- Incorrect nucleotide is inserted during replication
- The mismatched base is not repaired and gets replicated
In step 1 it’s just a lesion/mismatch
In step 2 it’s a mutation
What is the teg-1 gene
A gene that when mitated causes tumour enhancement and over proliferation of mitotic cells
What is the mutation in teg-1 (oz230)
What is the mitation called
The AAG changed to UAG at codon 53 (position 257) , this causes a premature stop codon
Since UAG, called amber
What is the mutation in teg-1 (oz189)
What is the mitation called
UGG to UGA at codon 142
UGA means opal