USE OF DNA TECHNOLOGY:

DNA PROFILING

USES OF DNA TECHNOLOGY

• DNA Profiling• Parentage Testing• Genealogy • Genetic Screening • Genetically Modified Organisms

DNA PROFILING

• Method to identify an individual based upon their DNA

• Used in:• Criminal investigations• Parentage Testing

UNDERLYING PRINCIPLE

• Over 99.9% of our DNA is identical across all people• BUT this means some is different

UNDERLYING PRINCIPLE• In our different DNA:• Variable number tandem repeats (VNTRs)• DNA made up of repetitive sequences that can

be found in different numbers for different people • STRs: short tandem repeats (2-5nt long)• LTRs: long tandem repeats

UNDERLYING PRINCIPLE

UNDERLYING PRINCIPLE

• VNTRs:• Are genetic…• The number of repeats in any given VNTR

would have been passed down from a parent

UNDERLYING PRINCIPLE• VNTRs:• Are very numerous in our genome• Take home message:• The number of repeats in each VNTR is unique

amongst individuals (unless identical twins)• You share roughly 50% of these repeats in

common with your parents and siblings

DNA PROFILING OVERVIEW

• Uses PCR to amplify VNTRs and then gel electrophoresis to visualize the DNA fragments created• This creates a unique DNA profile for each

person

DNA PROFILING: PCR

• Primers are designed to “bookend” a VNTR of interest• Primers need to anneal to a conserved region

of DNA that is identical to each person

UNDERLYING PRINCIPLE

DNA PROFILING: PCR

• Primers are designed to “bookend” a VNTR of interest• Primers need to anneal to a conserved region of

DNA that is identical to each person• PCR will therefore give different fragments lengths

based on how many repeats a person has

DNA PROFILING: GEL ELECTROPHORESIS

• After the PCR, DNA is run on a gel to visualize the lengths of the DNA products

UNDERLYING PRINCIPLE

DNA PROFILING

• To accurately identify a person and reduce false positives:• U.S. examines 13 separate VNTRs• UK has a system with 11 VNTRs

• Both of these have VNTRs that are found on different chromosomes• Think “Law of Independent Assortment”

DNA PROFILING

• Criminal Investigations:• Identifying who an

unknown DNA sample belongs to

DNA PROFILING

• Paternity Testing:• Identifying who the

father/parents of a child are