Mutations and Genetic Analysis Flashcards
What are the 3 types of chromosomal abnormalities?
- numerical
- structural
- mutational
What happens to most foetuses which have chromosomal abnormalities?
first trimester miscarriage
What type of chromosomal abnormality accounts for 50% of first trimester miscarriages?
Trisomy
Name a monosomy syndrome?
Turner syndrome, 45 X
What are 3 trisomy syndromes?
- Patau 47,XX+13
- Edwards 47,XY+18
- Down 47,XX+21
What is the chromosome complement of Klinefelter Syndrome?
47,XXY
Where do most cases of non-disjunction originate?
In the mother
What are the characteristic of Down’s Syndrome?
- characteristic facial dysmorphologies
- IQ less than 50
- Average life expectancy 50-60 years
- Alzheimer’s disease in later life
- Usually a result of maternal non-disjunction (also unbalanced Robertsonian translocation and Mosaicism)
What are the characteristic of Patau Syndrome?
- multiple dysmorphic features and mental retardation
- Very few survive beyond first year
- usually a result of maternal non-disjunction (also unbalanced Robersonian translocation)
What are the characteristics of Edwards Syndrome?
- severe developmental problems; most patients die within first year
- usually caused by maternal non-disjunction
What are 2 examples of sex chromosome aneuploidy syndromes?
- Turner Syndrome
- Klinefelter Syndrome
What are the characteristics of Turner Syndrome?
- mainly result in miscarriage
- females of short stature and infertile
- neck webbing and widely spaced nipples
- intelligence and lifespan is normal
What are the characteristics of Klinefelter syndrome?
- tall stature, long limbs
- male but infertile, small tested, about 50% gynaecomastia
- mild learning difficulties
What does structural abnormalities include?
- balanced or unbalanced rearrangements
- translocations
- deletions
- insertions
- inversions
What are the 2 kinds of translocation?
- Reciprocal: involving breaks in 2 chromosomes with formation of 2 new derivative chromosomes
- Robersonian: fusion of two acrocentric chromosomes
What types of mutation are there?
- non-coding
- coding which can be silent, missense, nonsense, frameshift (deletion/insertion)
What point mutations exist?
- transitions
- transversions
What is a transition mutation?
- A mutation which changes a purine nucleotide to another purine nucleotide A>G
OR
A mutation which changes a pyrimidine nucleotide to another pyrimidine nucleotide C>T
What is a transversion mutations?
A substation of purine for a pyrimidine A>C
OR
A substitution of pyrimidine for a purine C>G
How can mutations be detected?
- polymerase chain reaction (PCR)
- gel electrophoresis
- restriction fragment length polymorphism (RFLP) analysis
- amplification refractory mutation system (ARMS)
- DNA sequencing
What is needed for PCR?
- sequence information
- oglionucleotide
- DNA
- nucleotides
- DNA polymerase
What 3 steps are repeated in PCR?
- denature
- anneal
- extend
Describe gel electrophoresis.
- separate DNA fragments
- apply an electrical field
- DNA is negatively charged
- separate through agarose gel matrix
- visualise DNA fragments
What are the advantages of gel electrophoresis?
- speed
- ease of use
- sensitive
- robust
What can PCR be used for?
- DNA cloning
- DNA sequencing
- In vitro mutagenesis
- gene identification
- gene expression studies
- forensic medicine
- typing genetic markers
- detection of mutations
What are the advantages/disadvantages of ARMS?
- Advantages= cheap, labelling not required
- Disadvantages= electrophoresis required, primer design critical, need sequence information, limited amplification size, limited amounts of product, infidelity of DNA replication
What are restriction endonucleases?
- enzymes from bacterial cells that provide a protective mechanism by degrading DNA of invading viruses.
- they recognise specific DNA sequences, usually 4-8 bp long and always cut DNA at the same site
What are the advantages/disadvantages of RFLP?
- advantages= simple, cheap, non-radioactive
- disadvantages= requires gel electrophoresis, not always feasible
How can DNA be sequenced?
- chain termination method
- use of dideoxynucleotides
What are the advantages/ limitations of DNA sequencing by Sanger?
-advantages= mutation detection, automation and high throughput, next generation sequencing limitations= expensive equipment, poor quality sequence read
