Flashcards in Mutations and Genetic Analysis Deck (30):
What are the 3 types of chromosomal abnormalities?
What happens to most foetuses which have chromosomal abnormalities?
first trimester miscarriage
What type of chromosomal abnormality accounts for 50% of first trimester miscarriages?
Name a monosomy syndrome?
Turner syndrome, 45 X
What are 3 trisomy syndromes?
What is the chromosome complement of Klinefelter Syndrome?
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?
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
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?
-coding which can be silent, missense, nonsense, frameshift (deletion/insertion)
What point mutations exist?
What is a transition mutation?
- A mutation which changes a purine nucleotide to another purine nucleotide A>G
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
A substitution of pyrimidine for a purine C>G
How can mutations be detected?
-polymerase chain reaction (PCR)
-restriction fragment length polymorphism (RFLP) analysis
-amplification refractory mutation system (ARMS)
What is needed for PCR?
What 3 steps are repeated in PCR?
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?
-ease of use
What can PCR be used for?
-In vitro mutagenesis
-gene expression studies
-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