Topic 8 Flashcards
What are the types of dna variation
Snps (single nucleotide polymorphisms)
Indels (insertion-deletion)
STR (short tandem repeats)
What is an snp
Single base pair difference between dna sequences
(1 Nucleotide in top strand changes, so bottom strand also change)
What is a transition snp
A pyrimidine (ct) replaced with pyrimidine (ct)
Or purine to purine
Ex. C change to t
A to g
What is a trans version
Purine turns to pyrimidine
Or pyrimidine to purine
Ex. A to t
G to c
A to c
G to t
What are the causes of snp
- Spontaneous replication error (mismatching): due to tautomerization
- Natural Chemical changes to nucleotide: depurination, deamination
- Induced mutations: exposure to chemical mutagens like uv. Can replaced or alter a nuclotide
What is tautomerization
The position of the nucleotides atoms and bond between its atoms changes
Cause it to bind with diff base pairs
What is depurination
Hydrolysis of the bond between the purine nucleotide and the sugar of the backbone.
Loss of the purine which causes apurinic site where either no base is added or a diff base is added causing mutation
What is deamination
Removal of an amino group which is present in C A and G
How are mismatch errors fixed
3-5 exonuclease activity where the polymerase works backward to remove mismatch base
What is an insertion
A non repeating indel
Point mutation
Insterts a base into the sequence
Framshift
What’s a deletion
Framshift to the left
Removes a base
What happens if three nucleotide are deleted
No frameshift, just no more of that amino acid
What are strs
Short tandem repeats
Repeats of 2-9 nucleotides.
If person had 1000 ag repeats, still are because it’s repeat of two nucleotides
What is another name for str
Where can strs be found
Microsatallite
In introns exons regulatory regions and nonfunctional dna
Have high mutation rate
How many diff alleles can a snp cause
What about str
Max 4 (a t g c changes)
20+ (causes more variation)