Define:
DNA profiling
Genome
DNA Profiling: Producing an image of pattens in the non-coding DNA of individuals (way to identify DNA)
Genome: All genetic material in an organism (DNA & mitochondria)
Define:
Introns
Exons
Telomere
Exons: The coding regions of your DNA (a very small proportion compared with introns)
Introns: Large non-coding regions of DNA that are removed from mRNA before translation
Telomere: Region of repetitive nucleotide sequence at the end of a chromosome
Role: To prevent ends of chromosomes sticking together and to prevent from deterioration
What is satellite DNA and its types?
Satellite DNA: Short sequences of DNA that are repeated several times
Minisatellite: 20-50bp repeated 50 to several 100 times (aka VNTR)
Microsatellite: 2-4bp repeated 5-15 times (STR – short tandem repeat)
What does DNA profiling use to greate a genetic fingerprint?
- DNA profiling relies on short, repeating DNA sequences found in non-coding regions
- Within the non-coding regions are repeating sequences of DNA called VNTR (variable number tandem repeats)
- The variable number refers to the varying number of repeats of DNA
- VNTRs are found at the same 1000 different loci on the human genome, however in each individual the number of repeats vary
- Therefore, everyone has their own unique satellite pattern
- Producing an image of patterns in DNA is known as DNA profiling
What are the uses of DNA profiling in forensic science?
- Identify people involved at the scene of a crime by comparing traces of DNA from: blood, semen, hair, saliva, skin to DNA profiles of known criminals on a database
- The evidence can be used to prove innocence or guilt
- Can be used to identify body parts
What are the uses of DNA profiling in:
Analysis of disease risk
Other general uses
Other uses
- Prove paternity of a child
- In immigration to prove/disprove family relationships
In analysis of disease risk
- Identifying individuals at risk from developing diseases based on non-coding microsatellites
- Genetic screening for genetic disorder
- Presymptomatic testing for someone who has a family member with genetic disorder, but is asymptomatic themselves
What is PCR and what does it require?
Polymerase Chain Reaction
- A chemical process that replicates DNA from the smallest original sample
Requires: Small DNA sample; DNA polymerase; Primers; Nucleotides; Thermocycler
What are the first 2 stages of PCR?
Stage 1 – Denaturation (separating strands)
- DNA fragments, extra DNA nucleotides and DNA polymerase are added to the thermal cycles
- Heat to 95⁰Cto denature the DNA bybreaking hydrogen bonds holding the strands together
- The strands separate
Stage 2 – Annealing Primers
- Cool to 55⁰Cand theprimers (short single stranded DNA that begins extension of DNA strand)
- Provides starting point for DNA polymerase
What is the 3rd stage of PCR?
- Temperature raised to 72⁰C, optimum temperature for taq polymerase (from bacteria in hydrothermal vents)
- The DNA polymerase add bases complementarily to the primer to build a complementary strand
- The process is repeated again from stage 1 making several copies of the original DNA
What are the applications of PCR?
Tissue Typing: Helps match donor and recipient tissues to reduce risk of rejection
Detection of oncogenes: Detect type of mutation that could lead to cancer, can inform medication
Detecting mutations: Detecting genetic diseases, parents may do this before conceiving
Identifying viral infections: Verify type of virus present
Monitoring spread of infectious disease: Also monitoring emergence of new strains
Forensic science: Small quantities of DNA can be amplified to identify criminals ascertain parentage
Research: Amplifying DNA from extinct organisms
