BCH3031 Lecture Notes - Lecture 14: Cystic Fibrosis, Coagulopathy, Exome Sequencing
25 May 2018
School
Department
Course
Professor
Timothy Cole – Genomic Techniques to Understand and Model Human Disease
Lecture 14 – Analysis of Human Genetic Diseases and Genetic Testing of
Individuals and Populations
Mutations in DNA/genomes/OMIM database
• Some but not all mutatiosn cause disease
o Simple sequence variation (inversions, deletions)
• Loss of function mutation: reduced or no function of protein
• Gain of function mutation: positive function but abnormal – increasing
activity enzyme
• Single human gene disorders
o E.g. cystic fibrosis, DMD
• Polygenic disorders
o >1 genes (most cancers)
• Multifactorial disorders
o Complex genetics plus environmental factors
o Eg. Insulin dependent diabetes
Mutation in mapping strategies: positional genes
1. Position-independent strategies – functional cloning
• Haemophilia A (blood clotting disorder) (factor 8 deficiency)
o Purified factor 8 – generated antibodies to find gene
2. Positional gene coding – expensive/time
• E.g. cystic fibrosis gene
• Isolated common disorders – use of satellite markers to find regions of
chromosome: CFTR gene, localised on chromosome 7q31
• Cystic Fibrosis
o Autosomal recessive disease
o Chronic pulmonary disease
o Pancreatic insufficiency
o Male infertility
o Usually die ~30 years
• Mapping/cloning strategy
o Linkage studies using RFLPs and polymorphic markers in
families
o Contig mapping – chromosome walking and jumping with
genomic library
o Probe cDNA libraries developed from mRNA of target tissues
3. Positional candidate gene approach – of specific gene/gene region
• Required human genome sequence
• Using micro satellite markers – sequencing of human genome
• Complete inability to sense pain – caused by SCN9A
o OMIM 243000: autosomal recessive congenital
4. NGS: WGS and Exome Sequencing
• Traditional: DNA termination/capillary (Sanger) sequencers – ABI
sequencers
• Needed fast, cheap and high fidelity
o Fragment genome simultaneously
• Sequencing individual genomes
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