Genetic fingerprinting:
The analysis of VNTR DNA fragments.
VNTRs - variable number tandem repeats, found in the introns of human DNA
The probability of two individuals having the same VNTRs is incredibly low, but the more
closely related, the more similar your VNTRs are.
Collection - select and extract the DNA sample (if the DNA sample is small then a PCR
test is used to amplify the amount of DNA).
Extraction - restriction endonucleases are added to cut the DNA into smaller fragments.
Enzymes (restriction endonucleases) with a complimentary shaped active site to the
VNTRs are added.
Digestion - the DNA samples are loaded into small wells into agar gel. The gel is placed in
a buffer liquid with an electrical voltage applied. The DNA is negatively charged, so it
moves through towards the positive end of the gel.
Separation - this stage is gel electrophoresis. The agar gel creates resistance for moving
DNA, and the smaller pieces of DNA can move faster and further along the gel. This is
how different lengths of DNA are separated. An alkaline is then added to separate the
double strands of DNA.
Hybridisation - different DNA probes are mixed with the single stranded DNA VNTRs on
the agar gel for them to bind. DNA probes are short, single stranded pieces of DNA
complementary in base sequence to the VNTRs. The probes are radioactively or
fluorescently labelled.
Development - the agar gel will shrink and crack as it dries, and therefore the VNTRs and
DNA probes are transferred to a nylon sheet. The nylon sheet can then be exposed to x-
rays to visualise the position of radioactive gene probes, or UV light if fluorescent probes
were used.
Analysis - the position of the DNA bands are completed to identify genetic relationships,
the presences of a disease causing gene and to match unknown samples from a crime
scene.
The analysis of VNTR DNA fragments.
VNTRs - variable number tandem repeats, found in the introns of human DNA
The probability of two individuals having the same VNTRs is incredibly low, but the more
closely related, the more similar your VNTRs are.
Collection - select and extract the DNA sample (if the DNA sample is small then a PCR
test is used to amplify the amount of DNA).
Extraction - restriction endonucleases are added to cut the DNA into smaller fragments.
Enzymes (restriction endonucleases) with a complimentary shaped active site to the
VNTRs are added.
Digestion - the DNA samples are loaded into small wells into agar gel. The gel is placed in
a buffer liquid with an electrical voltage applied. The DNA is negatively charged, so it
moves through towards the positive end of the gel.
Separation - this stage is gel electrophoresis. The agar gel creates resistance for moving
DNA, and the smaller pieces of DNA can move faster and further along the gel. This is
how different lengths of DNA are separated. An alkaline is then added to separate the
double strands of DNA.
Hybridisation - different DNA probes are mixed with the single stranded DNA VNTRs on
the agar gel for them to bind. DNA probes are short, single stranded pieces of DNA
complementary in base sequence to the VNTRs. The probes are radioactively or
fluorescently labelled.
Development - the agar gel will shrink and crack as it dries, and therefore the VNTRs and
DNA probes are transferred to a nylon sheet. The nylon sheet can then be exposed to x-
rays to visualise the position of radioactive gene probes, or UV light if fluorescent probes
were used.
Analysis - the position of the DNA bands are completed to identify genetic relationships,
the presences of a disease causing gene and to match unknown samples from a crime
scene.
