The Control of Gene Expression: Gene Technologies - Genetic Fingerprinting Flashcards
What is genetic fingerprinting?
- A technique used to genetically identify an organism
- Has applications in forensics, paternity testing, diagnostics and the breeding of plants and animals
Does all of an organism’s genome code for proteins? What are genes that don’t code for proteins called?
- No, not all of an organism’s genome codes for proteins
- An organism’s genome contains many variable number tandem repeats (VNTRs)
- VNTRs are base sequences that don’t code for proteins
- They repeat next to each other multiple times
Why can VNTRs be used in genetic fingerprinting?
- The number of times VNTRs are repeated differs from person to person
- The probability of two individuals having the same VNTRs is very low
- The number of times the VNTR is repeated can be compared between individuals
How is a genetic fingerprint made?
• PCR is used to make DNA fragments
- Sample of DNA is obtained
- Primers used to bind to either side of repeats so whole repeat is amplified so length of DNA corresponds to number of repeats person has
- Fluorescent tag is added to all DNA fragments so they can be seen under UV light
• Separation of DNA fragments by gel electrophoresis
- An electric current is passed through gel
- DNA fragments are negatively charged so move towards positive electrode
- Shorter DNA fragments move faster and further through gel, so fragments separate according to length
- This produces a pattern of bands
How is a genetic fingerprint analysed?
- After gel has been running long enough, equipment is turned off and gel placed under UV light
- DNA fragments seen as bands under UV
- A DNA ladder may be added to one well (mixture of DNA of known length)
- If both fingerprints have band at same location on gel it means they have same number of nucleotides and VNTRs at that place
What is genetic fingerprinting used for?
- Determining genetic relationships
- Determining genetic variability within a population
- In forensic science
- For medical diagnosis
- In animal and plant breeding
How is genetic fingerprinting used in determining genetic relationships?
- We inherit VNTR bases from our parents: roughly half of the sequences come from each parent
- The more bands on a genetic fingerprint that match, the more closely related the people are
- Can be used to see if a population descended from a certain place
- If only tracing female line of descent, look at DNA in mitochondria (mtDNA typically only inherited from mother)
- If only tracing male side, look at Y chromosome DNA
How is genetic fingerprinting used to determine genetic variability within a population?
- The greater the number of bands that don’t match on a genetic fingerprint, the more genetically different the individuals are
- Can compare the number of VNTRs at several places in genome for a population to find how genetically varied that population is
How is genetic fingerprinting used in forensic science?
- Forensic scientists use genetic fingerprinting to compare samples of DNA collected from crime scenes to samples of DNA from suspects
- DNA isolated from sample
- Each sample replicated using PCR
- PCR products ran on electrophoresis gel
- Genetic fingerprints used to see if any match
How is genetic fingerprinting used in medical diagnosis?
- A genetic fingerprint can be used to diagnose genetic disorders and cancer
• Preimplantation genetic haplotyping (PGH)
- Screens embryos created by IVF for genetic disorders before implanted into uterus
- Faulty regions of parent’s DNA used to produce genetic fingerprints
- If fingerprints match, embryo has inherited disorder and may not be implanted
How is genetic fingerprinting used in plant and animal breeding?
- Genetic fingerprinting used to prevent inbreeding
- Inbreeding can lead to increased risk of genetic disorders leading to health, productivity and reproductive problems
- Animal breeders can select animals to mate which aren’t closely related
