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diagnostic DNA - Coggle Diagram
diagnostic DNA
DNA as a diagnostic tool
DNA profiling
confirms parenting
DNA fingerprinting
forensic analysis
Diagnostic DNA tests
diagnose genetic variant with disease
screening for pre-disposition to disorders
selection of desirable traits in livestock
sample origin and preparation
important DNA properties
neg charged
soluble in water
insoluble in ethanol
cells can be lysed in aqueous buffers --> DNA extracted and isolated with ethanol
sample origins
easiest: peripheral blood
for RNA studies: skin
often invasive and painful
needs to be tissue where gene is expressed
DNA testing at genomic/chromosomal level
karyotyping
is chromosome number correct?
is chromosome structure correct?
*can only distinguish large deletions/duplications
array comparative genomic hybridisation
sample and normal DNA labelled and hybridised
equal numbers of copies of sequences --> yellow
more sample than reference --> red
less copies of sample DNA than normal--> green
can detect deletions or duplications in a section of DNA
pre-implantation genetic diagnosis
performed in conjunction with IVF from parents with genetic disorder
1-2 cells from embryo removed
dna isolated and tested for mutation/chromosomal abnormality
normal embryo implanted, mutated embryo discarded
DNA testing at molecular/nucleotide level
VNTR polymorphisms, DNA fingerprinting
genome contains large numbers of microsatellite repeat sequences
microsatellites variable between individuals, can use to identify individuals or parentage
isolate DNA from samples
break into small fragments
with restriction enzymes
electrophoresis to separate size
blot gel into membrane
incubate with radioactive probe that binds VNTR sequences only
where probe bound exposes onto film --> bands shown
polymerase chain reaction
denaturation, primers anneal, primers elongate, repeat
restriction fragment length polymorphisms
uses enzymes which recognise specific DNA sequences and cleave DNA at recognition site
mutation leaves DNA fragment uncut, or cuts at unexpected places
restrictions
need to know sequence at either side of mutation site
need to know mutation
mutation needs to be in restriction site
different enzymne needed for each mutation
DNA sequencing: Sanger Method
limitations
can only read a short length (2-3 exons)
error prone
need to sequence repeatedly to ensure correct sequences
next generation sequencing
exome sequencing
sequencing all exons
transcriptome sequencing
sequences all RNA in a cell
whole genome sequencing
sequences entire DNA of individual
limitations
huge amounts of data generated
requires special software
big variation between individuals
exome sequencing: variants only identified in protein coding sequences