Fergus - Lecture 2 Flashcards
What are the different branches of medical genetics?
Clinical genetics
Molecular genetics
cytogenetics
What are clinical genetics?
Diagnostics of genetic disorders and genetic counseling for individuals or families with or at risk of conditions with a genetic basis
What is cytogenetics?
How chromosomes relate to cell behaviour, particulary to their behaviour during mitosis and meiosis
What is molecular genetics?
The manipulation of an organism’s genome
What is medical genetics responsible for?
(4)
Diagnosis -> clinical or laboratory
Carrier detection -> pedigree analysis or lab analysis
Predictive testing -> pre-symptomatic diagnosis by DNA analysis
Genetic counselling
What does ARMS stand for?
Amplification
Resistant
Mutation
System
What is an ARMS PCR also known as?
Allele specific PCR
How does an ARMS PCR work?
(5)
Primers are designed to amplify only the normal or only the mutated sequence
Based on the 3’ nucleotide of the primer matching exactly the target or mismatched
2 PCR reactions are performed
Normal primer, Mutation primer and common primer
The normal primer will only work on a normal sequence and a mutated primer will only work on a mutated sequence
How many primers are needed for an ARMS PCR?
Three
Common, normal, mutated
What is real time PCR?
(4)
PCR where we can detect products as they are being generate using fluorescent labelling
Dependent on fluorescent detection of PCR products during cycle
Two types: specific or non-specific
Non specific: DNA is split into single strands, fluorescent dyes are attached - the intensity of the fluorescence is measured
Specific: olgionucleotide probes labelled with fluorescent reporters, which permits detection only after hybridization of the probe with its complementary sequence
What does SSCP stand for?
Single strand conformation polymorphism
What is the basis of SSCP
Single-stranded DNA has a defined conformation
If mutated the single-stranded DNA will migrate differently during
Therefore mutant DNA samples display different band patterns.
Write a note on fragile X chromosome
(5)
Most common form of male intellectual disability
Mutation in FMR1 gene
RNA binding protein associated with polyribosomes
Fragile site at Xq27
Incidence of 1/2000 males
What causes fragile X?
(3)
Part of the long arm of chromosome X is damaged ‘fragile’ in affected males
Its caused by a mutation in the FMR1 gene located at Xq27
It affects an RNA binding protein associated with polyribosomes
Can fragile X affect females?
It can cause a slight drop in IQ in females
What type of mutation causes fragile X?
(3)
A trinucleotide repeat (CGG)
On the 5’ untranslated region of the FMR1 gene
Between 50 and 200 repeats
What happens if you have 170 CGG repeats or over 200 CGG repeats?
(2)
Fragile X
Methylation of the promoter resulting in failure of the FMR1 gene
The presence of what can help stabilise the FMR1 gene?
The presence of As in the sequence
What happens if you have 34 repeats in huntingtons?
You are normal
>35
What happens if you have 36 repeats in huntingtons?
You have huntingtons
What happens if you have 39 repeats in huntingtons?
You will die
Write a note on polyposis colon cancer
(5)
Dominant
1 in 10,000
mutation in APC gene
Mutation results in truncated protein
Detected using PTT
What is PTT?
Protein truncating test
