Genetic Fingerprinting Flashcards
(27 cards)
What is 95% of DNA made up of?
Introns
What do introns consist of?
Many variable number tandem repeats
What does VNTRs stand for?
Variable number tandem repeats
What are introns?
The NON-CODING regions of your DNA
What is the probability of two individuals having the same VNTRs?
Very low
What is the relationship between relation and similarity of VNTRs?
The more closely related you are, the more similar the VNTRs are
What is genetic fingerprinting?
The analysis of VNTR DNA fragments
What can genetic fingerprinting be used for?
Used to determine genetic relationships and the genetic variability within a population
What are the 7 stages that the process of genetic fingerprinting can be separated into?
- Collection
- Extraction
- Digestion
- Separation
- Hybridisation
- Development
- Analysis
What size does the DNA sample have to be for genetic fingerprinting?
It can be the smallest sample of DNA
What samples can you collect the DNA from for use in genetic fingerprinting?
Blood, body cells, hair follicles
If the sample of DNA is small then what has to be done?
Then PCR is used to amplify the amount of DNA
Describe the ‘digestion’ stage of genetic fingerprinting:
Once we have a larger sample, restriction endonucleases are added to cut the DNA into smaller fragments. Make sure to select restriction endonucleases that have a complementary active site to the sequence which is found just before the VNTRs. Ensures you have the entire length of the VNTR maintained.
Describe the ‘separation’ stage of genetic fingerprinting:
The DNA samples are loaded into small wells in agar gel. The gel is placed in a buffer liquid with an electrical voltage applied
DNA is negatively charged, so the DNA samples move through the agar gel towards the positive end of the gel.
What charge does DNA have and why?
DNA is negatively charged because the oxygens within the phosphate group are negative
What process happens during the separation stage of genetic fingerprinting?
Gel electrophoresis
During gel electrophoresis, what is added to separate the double strands of DNA?
An alkaline solution
How are the different lengths of DNA (VNTRs) separated?
Because the gel creates resistance for the moving DNA and smaller pieces of DNA move faster and further along the gel.
Describe the ‘hybridisation’ stage of genetic fingerprinting:
This is why we needed single stranded DNA
Lots of different DNA probes which are either radioactively/fluorescently labelled are mixed with the single stranded DNA VNTRs on the agar gel. The DNA probes that are complementary in base sequence to the VNTRs will bind (HYBRIDISE)
We then rinse the gel to make sure that any DNA probes that didn’t bind are washed away.
What is a DNA probe?
A short, single stranded piece of DNA which is complementary in base sequence to anything, e.g. VNTRs (in this case)
Describe the ‘development’ stage of genetic fingerprinting:
The agar gel will shrink and crack as it dries (once removed from liquid), therefore the VNTRs and DNA probes are transferred to a nylon sheet.
The nylon sheet is then exposed to X-rays (if it was a radioactive probe) in order to visualise the position of the radioactive DNA probes
UV light is used instead if fluorescence probes were used.
Describe the ‘analysis’ stage of genetic fingerprinting:
The position of the DNA bands are compared to identify genetic relationships, the presence of a disease causing gene or to match unknown samples from a crime scene.
What can gel electrophoresis be used for?
Paternity test analysis
What 3 fields can genetic fingerprinting be used in?
Forensic Science, suspects DNA at crime scene
For medical diagnosis
To ensure animal and plants are not closely related before being bred (animal and plant breeding)
