DNA
Fingerprinting
Introduction
Ø
DNA fingerprinting is a groundbreaking method
used to identify individuals by analyzing unique patterns in their DNA.
Ø
DNA fingerprinting, also known as DNA profiling,
is a method used to identify individuals based on their unique DNA
characteristics. This technique has become an essential tool in forensic
science, allowing for the identification of individuals involved in crimes.
Ø
The process focuses on variable number tandem
repeats (VNTRs) or other polymorphic regions in the genome, particularly in the
non-coding parts of DNA.
Ø
Although these regions do not code for proteins,
they exhibit a high degree of variation from one person to another.
Steps of DNA Fingerprinting (DNA Fingerprinting Steps)
- DNA
Isolation
- Scientists
collect a sample (e.g., from blood, hair follicles, saliva).
- The
cells are broken open, and DNA is carefully extracted and purified.
- Digestion
with Restriction Enzymes
- Special
proteins known as restriction endonucleases are used to cut the DNA at
specific sequences.
- This
creates fragments of varying lengths based on each individual’s unique
repeat patterns.
- Separation
by Electrophoresis
- The
DNA fragments are placed in a gel and subjected to an electric field.
- Smaller
fragments move faster through the gel, thus separating DNA fragments
according to size.
- Blotting
onto a Membrane
- The
separated fragments from the gel are transferred (blotted) onto a nylon
or nitrocellulose membrane.
- This
makes the DNA stable and accessible for further analysis.
- Hybridisation
with Labelled Probes
- Specific
VNTR or STR probes, often radioactively or fluorescently labelled, bind
to complementary sequences on the DNA fragments.
- These
probes highlight the areas of interest that display polymorphism.
- Autoradiography
(or Imaging)
- An
X-ray film or other imaging technique is used to detect the labelled
probes.
- The
result is a series of distinct bands unique to each individual, known as
the DNA fingerprint.
