Topic 8—B: Genome Projects and Gene Technologies- 7. Genetic fingerprinting Flashcards
1
Q
Does all of the organisms Genome code for proteins.
A
No
2
Q
What do some of the genome consist of?
A
- Variable number tandem repeats (VNTRs)
3
Q
What are variable number tandem repeats
A
- They are basic sequences that don’t code for proteins and repeat next to each other over and over
4
Q
Are the number of times these sequences repeated different from person to person or the same.
A
They are different
- so the length of these sequences in nucleotides differs to
5
Q
Where does the repeated sequences occur in lots of places?
A
In the genome
6
Q
Genetic fingerprinting
A
- The number of times a sequence is repeated at different places in the genome can be compared between individuals
7
Q
What is the probability of two individuals having the same genetic fingerprint and why?
A
Because the chance of two individuals having the same number of VNTRs each place they’re found in DNA is very low
8
Q
How is a genetic fingerprint made?
A
- PCR is used to make DNA fragments.
- Sample of DNA is obtained, e.g. From a persons blood, saliva, etc
- PCR is used to make many copies of the areas of DNA that contain the VNTRs
- Primers are used that bind to either side of these repeats and so the whole repeat is amplified (copied many times)
- Different primers are used for each position under investigation
- You end up with DNA fragments where the length (in nucleotides) correspond to the number of repeats the person has at each specific position, e.g. One person may have 80 nucleotides, another person 120
- Fluorescent tag is added to all the DNA fragments (usually to the primers) so they can be viewed under UV light - Separation of the DNA fragments by gel electrophoresis.
- to separate DNA fragments the DNA mixture is placed into a well in a slab of gel and covered in a buffer solution that conducts electricity
- An electrical current is passed through the gel- DNA fragments are negatively charged so they moved towards the positive electrode at the far end of the gel
- shorter DNA fragments move faster and travel further through the gel so the DNA fragments separate according to length
- this produces a pattern of bands - Analysis of the genetic fingerprints.
- After the gel has been running long enough, the equipment is turned off and the gel is placed under a UV light
- Under the UV light the DNA fragments can be seen as bands
- These bands make up the genetic fingerprint
- A DNA ladder may have been added to one well- this is a mixture of DNA fragments of known length that allows you to work out the length of the other bands on the gel
- two genetic fingerprints can be compared e.g. If both fingerprints have a band at the same location on the gel it means they have the same number of nucleotides and so the same number of. VNTRs at that place.- it’s a match
9
Q
Uses of genetic fingerprinting
A
- Determining genetic relationships.
- We inherit VNTR sequences from our parents
- roughly half of the sequences come from each parent
- This means the more bands on a genetic fingerprint that match, the more closely related (genetically similar) two people are
- Genetic fingerprinting can also be used to look at much wider ranging genetic relationships e.g. To see if a population of black bears found in Virginia is descended from a population in Canada or Alaska.
- The idea is still the same- the more bands the populations have in common the more closely related they are
- Sometimes you might be interested in tracing only the male or female line of descent
- To look at the female line of descent, you need to look at DNA in mitochondria
- This is because humans and other organisms mitochondrial DNA is only inherited from your mum
- If you’re after the mail, you need to look at Y chromosome DNA as only men have a Y chromosome - Determining genetic variability within a population
- The greater than number of bands that don’t match on a genetic fingerprint the more genetically different individuals are
- This means you can compare the number of repeats at several places in the genome for a population to find out how genetically varied that population is e.g. The more than number of repeats varies at several places the greater the genetic variability within a population. - In forensic science
- Forensic scientists use genetic fingerprinting to compare samples of DNA collected from crime scenes e.g. DNA from blood, semen, skin cell, saliva, hair)
- To samples of DNA from possible suspects which could link them to crime scenes
- The DNA is isolated from all the collected samples (from the crime scene and from the suspect)
- Each sample is replicated using PCR
- the PCR products are run on an electrophoresis gel and the genetic fingerprints produced compared to see if any match
- If the samples match it links a person to the crime scene - For medical diagnosis.
In medical diagnosis and genetic fingerprint can refer to a unique pattern of several alleles
- It can be used to diagnose genetic disorders and cancer
- It’s useful when the specific mutation is known or where several mutations could have caused a disorder because it identifies a broader altered genetic pattern - In animal and plant breeding.
- Genetic fingerprinting can be used on animals and plants to prevent in breeding which decreases the gene pool (the number of different alleles in population)
- Inbreeding can lead to an increased risk of genetic disorders, leading to health, productivity and reproductive problems
- Since genetic fingerprinting can be used to identify how closely related individuals are it can be used to identify the least related individuals in a population so that we can breed them together
- Genetic fingerprinting can also be used by animal breeders to prove pedigree (who animals and descendants are)
- animals With a good pedigree will sell for more money e.g. The offspring of craft or Grand National winners can sell for a lot of money if you can prove their pedigree.
