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Genetic Fingerprinting (DNA Profiling) - Coggle Diagram
Genetic Fingerprinting
(DNA Profiling)
What does it do?
analysing and comparing the
DNA of individuals
uses
restriction endonucleases
to
cut
satellite repeat sequences
from the DNA
which is then detected using
DNA probes
Uses
settle paternity
disputes
establish family relationships
study genetic diversity
of species
forensic science
establish identity of:
corpse
criminal suspect
Technique based on...
95% of DNA does not code for proteins
introns contain sequences of bases
that repeat over + over again
we
inherit
distinctive combination of
core/repeated sequences
half from mother
half from father
1. Extraction
DNA
extracted
from sample blood/tissue
contain DNA of 2 sets of chromosomes
(from mum, 1 from dad)
if sample size small -
amplified using PCR
2. Digestion
DNA cut into fragments
using restriction endonuclease enzymes
cut close to groups of core sequences
3. Separation -
Gel Electrophoresis
fragments added to agarose gel
separated by size
using gel electrophoresis
smaller fragments move further
4. Transfer
STEP 1
double stranded fragments
treated with alkali
produce single strands
STEP 2
single strands transferred from gel
onto nylon membrane
technique -
Southern Blotting
:
lay thin sheet of nylon over gel
cover with several sheets of absorbent gel
draw up liquid containing DNA
transfer fragments from gel to membrane
in EXACT same position on gel
fix fragments to membrane using UV light
5. Hybridisation
membrane
washed
with:
fluorescent
or radioactive labelled DNA probes
(with base sequences complementary to core sequence)
hybridise
(bind) to these fragments
via base pairing rules.
many probes added + each bind with
different core sequences
excess probes that did not bind
are washed away
6. Development
x ray film
placed over nylon membrane
film is exposed by radiation from probe
only DNA fragments
with probes attached show up
points correspond to position of DNA fragments
pattern of bands is called a genetic (DNA) fingerprint (looks like a bar code)
pattern of bands unique for
every individual