Mutations and Genetic Analysis Flashcards
types of chromosomal abnormalities
- numerical - wrong no. chromo in karyotype (not 46)
- Structural - chromo rearranged/fused
- Mutational - smaller scale changes (deletion/single base pair mutation)
common type of chromosomal abnormality
Trisomy (about 50% in first trimester miscarriages across all types)
trisomy 21
down syndrome
origin of chromo abnormalities: non-disjunction
Occur in failure of disjunction of meiosis e.g. not 4 cells with 4 chromo but could be 2 with 1, 1 with 2 (disomy) and 1with none (null)
where is the origin of non-disjunction (apart from 45,X)
Maternal
aneuploidy
the condition of having an abnormal number of chromosomes in a haploid set
give 3 autosomal aneuploidy syndromes
- trisomy 21 (down syndrome)
- Trisomy 13 (patau syndrome)
- Trisomy 18 (Edwards syndrome)
trisomy 21 (down syndrome)
autosomal aneuploidy syndrome
- Inc with advancing maternal age (probs due to non-disjunction problems)
- low IQ
- Lower life expectancy
- Tendancy twoards Alzheimer’s in later life
- Chromosomal findings: non-dysjunction (95%) usualy maternal, unbalanced Robertsonian translocation (4%), Mosaicism (1%)
trisomy 13 patau syndrome
autosomal aneuploidy syndromes
- dysmorphic features and mental retardation
- very early death
- Non-dysjunction with maternal origin (90%), unbalanced robertsonian translocation (10%)
Trisomy 18 (edwards syndrome)
autosomal aneuploidy syndromes
- severe developmental problems - early death
- Non-dysjunction with maternal origin (90%)
give 2 sex chromosome aneuplodiy syndromes
- 45,X (turner syndrome) - only single X chromo: females short stature and infertile, neck webbing
- 47,XXY (Klinefelter syndrome): tall stature, long limbs, males infertile, mild learning difficulties
give some common chromosomal structural abnormalities
- balanced or unbalanced rearrangements
- Translocations (reciprocal or robertsonian)
- Deletions
- Insertions
- Inversions
reciprocal translocations
invilving breaks in 2 chromo with formation of 2 new derivative chromo
Robertsonian translocation
fusion of two acrocentric chromosomes - results in loss of short arms
acrocentric - centromere at ends of chromo
what is a key feature of a balanced translocation
No DNA lost
key feature of unbalanced translocation
a translocation between chromosomes resulting in the gain or loss of genetic material, likely resulting in a chromosomal condition
robertsonian translocation carrier outcomes
increased risk for infertility, spontaneous abortions, or chromosomally unbalanced offspring.
Deletion
break in chromosome and loss of genetic material
Inversion
Balanced rearrangements - no phenotypic effect
what 2 different things can mutations act on
non-coding or coding sequences
types of mutation acting of coding sequences
- silent (CGA arg to CGC arg)
- Missense (CGA arg to GGA glc)
- Nonsense (CGA arg to TGA stop)
- Frameshift (deletion/insertion)
how can we detect mutations
5
- PCR
- Gel electrophoresis
- Restriction fragment length polymorphism (RFLP) analysis
- Amplification refractory mutation system (ARMS)
- DNA sequencing
Things required for PCR
- sequnce info
- corresponding oligonucleotide primers
- DNA
- nucleotides
- DNA polymerase (thermally resistant)
PRC technique
(brief)
- Denature DNA
- Anneal (primers bind?)
- Extennd
summarise gel electrophoresis
- seperate DNA fragments bu size
- apply electric field
- DNA -vely charged
- Seperate by size through agarose gel matrix
- visualise DNA fragments
advantages of PCR
- speed
- ease of use
- sensitivity
- robuse
applications of PCR
just list a ton of em
- DNA cloning
- DNA sequencing
- In vitro mutagenesis
- Gene identification
- Gene expression studies
- Forensic medicine
- Typing genetic markers
- Detection of mutations
ARMS
name, what does it allow us to do?
amplification refractory mutatuon system - allows us to see if individual has mutation at specific site if we know what it is
Pros/cons of ARMS
Advantages:
* Cheap
* Labelling not required (flourecent, redioactive)
* Electrophoresis required
* Primer design critical
Disadvantages:
* need sequence information
* Limited amplification size
restriction endonucleases
family of enzymes that each recognise and cut DNA at a specific sequence recognition site
RFLP analysis
(Restriction fragment length polymorphism)
Enzyme can recognise/cut normal DNA but not mutated DNA - assay shows lines - lack of line = mutation
Pros/cons of RFLP
Advantages:
* Simple
* Cheap
* Non-redioactive
Disadvantages:
* Required gel electrophoresis
* Not always feasible
what does DNA sequencing rely on
OH group on deoxynucleotide - uses dideoxynucleotides
Advantages/limitations of DNA sequencing
Advantages:
* Great for mutation detection
* automation and high throughput
Limitations:
* Expensive equipment
* Poor quality sequence read (first part good then deteriorates at about 800 bases)
What factors would contribute to the ultimate test method
weird one but…
- direct test
- quick and easy
- cheap
- sensitive
- specific
