the summary starts with an introduction to SNPs, genetic variants and types of mutations. It includes a detailed summary of GWAS analysis. Genetics of neurological diseases such as Parkinson's, and Huntington's are introduced.
2- GENETICS OF NEUROLOGICAL DISEASE
Sunday, 1 October 2023 14:58
SNPs (Single Nucleotide Polymorphisms) : mutations established in the
population
Common genetic variation
A location on the DNA is A (adenosine) in 95% of humans - T (thymine) in 5% of
humans
This variant is called a SNP
It is important to understand a single difference of traits in humans
Helps understand what traits are genetic and what biological mechanisms in our
body might be affecting those traits
Structural variation
Deletions, insertions of segments of DNA
Line/sine elements
CODON: dna or rna sequence of 3 nucleotides forms a unit of genomic info
encoding a particular amino acid or signalling termination of protein synthesis
MUTATION TYPES:
FRAMESHIFT
- Deletion or insertion of nucleotides
AUG-AAU-ACG-GCU addition of A
Becomes AUG-AAA-UAC-GGC-U
Cause a shift in the reading frame
Alteration in sequence of amino acids in protein translation
MISSENSE
- Codon specifying a different amino acid
- Causes synthesis of a protein with an altered amino acid sequence in
translation
NONSENSE
- Does not code for amino acid, leads to a protein product that is early
shortened
- ATC --> UAG A and U cant be together thus, STOP
SILENT
- Codon codes for the same amino acid produces no structural nor
physiological change in protein product
NEUTRAL
- No selective advantage or disadvantage
, - ATC --> UAG A and U cant be together thus, STOP
SILENT
- Codon codes for the same amino acid produces no structural nor
physiological change in protein product
NEUTRAL
- No selective advantage or disadvantage
When the genome is copied to make a new cell, a single base pair gets left out,
added or substituted
Single base pair substitutions create = SNPs
There are many SNPs , they account for genetic differences in people
Some account for physical differences, some for the risk of disease or how we
react to drugs
Some don't make observable differences
Genetic mosaicism
Error in cell division in very early development of the unborn baby
Examples: mosaic down syndrome
INHERITANCE
Autosomal dominant: 50% chance of being affected
Autosomal recessive: requires two copies of the mutated gene from each parent
to cause disorder
To find disease linked changes:
Linkage analysis
- Detect the chromosomal location of disease genes
When two genes are close to each other on the chromosome and do not change
places during crossing over, linkage is formed
A/a and B/b exchange in crossing over but they don't in linkage
GWAS
What genes are causing a disease
What variants in our DNA might be impacting a trait
Process:
Large sample size (ideally the same ethnicity to minimize confounding genetic
variation)
Each person gets genotyped/ have their nucleotides recorded at many known
SNP locations
Record each persons trait/disease/phenotype
Association between the genotype and phenotype is computed
Via GWAS programme
Remove individuals and SNPs with faulty info
Regression analysis
Each individual is a data point
Example;
Reg analysis for SNP no 1 : A or T
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