Forensics DNA

Is DNA unique to each person?

• yes, no two people have the same DNA

• except for indentical twins

• individual evidence

How have advances in DNA technology impact criminal cases?

• have allowed criminal cases to be solved/ re-examined

Why is DNA considered to be individual evidence?

• DNA is unique to one person (except for identical twins)

DNA can be collected from what?

• skin

• blood

• saliva

• urine

• semen

• hair

DNA in forensics

• DNA profiling is used

• determines identity or parentage

What does DNA stand for?

deoxyribonucleic acid

Where is DNA located?

• in the nucleus of the cell

• carries an organisms genetic information

• also found in the mitochondria (mothers DNA)

What does DNA consist of?

• nucleotides

• has 3 parts phosphate group, sugar, base

What are the 4 types of bases/DNA?

• Thymine (T)

• Cytosine (C)

• Adenine (A)

• Guanine (G)

How do the bases correspond to each other?

• A goes with T

• C goes with G

What role does DNA play in forensics?

• matching DNA to a suspect or victim

• fairly new tech

• very useful form of evidence

What is CODIS?

• the national DNA database (like the fingerprint one)

DNA profiling

a process of analysis that reveals unique patterns of an individual’s DNA

• most important forensics discovery

non-coding regions of DNA

• depict a high level of polymorphism (variations in DNA sequences among individuals) (99% of our DNA is the same as each others)

• the 1%

Alec Jeffreys

• developed the process of DNA profiling

• 1984

• 1987 - first conviction based on DNA evidence

chromosomes

large entwined strands of DNA

alleles

• smaller sections of Chromosomes

• when common alleles are identified between two samples of DNA a positive match can be made

basic steps to gel electrophoresis/ DNA profiling

• DNA extraction

• purification and separation of DNA from the rest of the cell

• DNA cut into fragments by restriction enzymes

• amplify (make more) using PCR

• fragments separated using gel electrophoresis

What are some concerns regarding DNA profiling in forensics?

• quality of sample

• mistakes and inaccuracy

• cost effective

STR

• short tandem repeats

• looks like a bunch of peaks

How do you tell where an individual is homozygous when looking at STR?

• homozygous= same

• only one number/ peak

• heterozygous= different

• two numbers/peaks

What do the numbers below the peaks on STR graphs mean?

• the amount of times an allele repeats