WHAT IS DNA AND HOW CAN WE USE IT AS EVIDENCE? MAY 30, 2014
Dec 24, 2015
W H AT I S DNA AND H O W C A N W E US E I T A S E V I DE NC E ? M AY 30 , 2014
F I N D T H E D I F F E R E N C E S B E T W E E N T H E P H O T O S B E LO W
AG E N DA
• What is DNA?
• How is DNA Replicated?
• What type of evidence is DNA?
• How can we test DNA?
• Paternity Testing
R E M I N D E R S
• If you have not taken your test, you must take it today
• If you know you are failing the course, see me after class
• Check powerschool to see your grades
D N A • Deoxyribonucleic Acid
D N A• Major function is to provide
instructions for the cell to make proteins and copies of itself
• Like a cookbook, with instructions to make each part of the cell and everything it needs to work
• DNA is heritable (it gets passed on)
D N A A S E V I D E N C E
• Circumstantial and Individual
• Found in:
• Saliva
• Semen
• Blood
• Skin
• Urine
• Hair
D N A A S E V I D E N C E
• DNA can be used to link a suspect to a crime, identify a suspect, and identify remains.
• DNA fingerprinting is the technique used to identify people
• Most samples found at the scene of the crime are small, and must be amplified to be tested
G R E E N R I V E R K I L L E R
• Gary Ridgway
H TT P : / /W W W. B IO G RA P H Y. CO M /P E O P L E /G A RY- R ID G WAY- 1 0 07 3 4 0 9 / V ID E O S /G A RY- R ID G WAY- M IN I -B IO G RA P H Y- 2 1 6 5 7 6 47 0 4
D N A S T R U C T U R E
• Watson and Crick are credited with discovering the structure of DNA
D N A S T R U C T U R E
• DNA looks like a ladder, but is in the shape of a double helix
• This allows for improved storage and protection. Without this, mutations would occur frequently.
D N A S T R U C T U R E
• DNA’s backbone is made up of sugars and phosphates
• The rungs of the ladder are made up of bases that are in pairs
D N A S T R U C T U R E
• DNA has four bases that pair together in specific ways:
• Adenine (A)
• Thymine (T)
• Guanine (G)
• Cytosine (C)
• A with T and C with G
D N A S T R U C T U R E
• DNA Replicates by unzipping itself and making new copies (semiconservative replication)
D N A F I N G E R PR I N T I N G
• Individuals have unique sequences of repeated DNA patterns in the non-coding region of DNA (doesn’t become protein)
• Variations called polymorphisms
• Polymorphisms give each person a unique DNA fingerprint
• Different sequences are seen in the genome of an individual (entire genetic code)
• Two type of repeats used are VNTR and STR
D N A F I N G E R PR I N T I N G
• VNTR
• Variable Number of Tandem Repeats
• 9 to 80 bases long
D N A F I N G E R PR I N T I N G
• STR
• Short Tandem Repeats
• 2 to 5 bases long
• Easier to use
S T E P S I N D N A F I N G E R P R I N T I N G
1. Extraction
2. PCR
3. Gel Electrophoresis