SNPs Flashcards
Transitions vs transversions (mutations)
transitions : purines and pyrimidine changes within group
More common, because they are harder to catch
Transversion:
purine to pyramidine mutation (or vice versa)
Genetic identity for 2 unrelated people
2 unrelated people share approx 99.5% identity
WGS
whole genome sequencing
synonymous vs non synonymous mutations
Synonymous mutations do not affect amino acid sequence
genetic bottleneck
when a population is reduced to the point where the offspring will have a limited gene pool
founder effect
where a small number of a species establish the population in a particular region. The offspring therefore have a small gene pool to work with
Denisovians
hominids that split off and contributed to polynesian populations, but not eurasian ones
HAPLOTYPE:
Linkage of different genetic differences to each other.
ALLELE:
Alternative form of a genetic locus (or gene). One of the two copies of a gene inherited from each parent
Why is sickle cell anaemia prevalent in certain populations ?
In a haploid state, the RBC will sickle when infected by malaria.
The positive effect is balanced by the negative heterozygous effect where it sickles at low pO2
Selection signal
A region of low variability that indicates gene selection.
Lactase expression past childhood is seen in what population ?
European and sub-Saharan Africa
At what frequency does a gene become fixed in a population ?
99%
It takes approx 200 generations (5000 years) to go from 1% to 99%
How do you know when a particular mutation / selective sweep took place ?
The local conservation of genes can be indicative of how recent the sweep took place.
A newer mutation will not have had time for local variation due to mutation, or crossing over, etc
What are “passenger SNPs”
They are genes adjacent to favourable genes in a selective sweep.
They are selected for by proximity.
What is Kuru?
It is the human form of CJD
Where is Kuru prevalent ?
It is prevalent in the Highland people of Papua New Guinea: the Fore people
They participate in cannibalistic rituals
What is a cline ?
It is a gradual change in rate in correlation with geographic or environmental transition
How does thioguanine monophosphate work (2 mechanisms)?
It causes repression of purine synthesis by pseudofeedback, or by incorporation into DNA, where it becomes methylated.
It arrests cell growth and induces apoptosis
What does thyoguanine monophosphate target, and why ?
It targets B and T cells, since they are dependent on the pathway.
Other cells have a “salvaging mechanism”
Theraputic Index
LD50 / ED50
or TD50 / ED50
What is the consequence of inactive TPMT
Thiopurine s-methyltransferase (TPMT) allows thiopurines to be metabolised
If absent or inactive, it can allow them to build up to toxicity
What is an odds ratio ?
It is the likelyhood of disease of people exposed to a risk factor (eg, gene) vs. non exposed
Odds ratio formula
OR=(Ie/Io)/(Ne/No)= Ie No / Io Ne
Where: OR = odds ratio Ie = disease and risk factor Io = disease and no risk factor Ne = no disease and risk factor No = no disease, no risk factor
Cisplatin use and toxicity
used in paediatric cancers
may cause deafness
