Forensic Sci Unit 4 DNA Fingerprinting

DNA

→ Purpose: Codes how to make you

→ Structure: Double Helix

→ Location: Nucleus

How much DNA do we share?

99%

How much DNA do we share is different?

0.1%

Is DNA Evidence Class or Individual?

Individual

CSI clothing

Protective gloves, booties, + outfits

→ Important to keep our evidence clean and true to prove that somebody committed a crime without questioning the science and forensic

Alec Jeffrey

1980: Invented DNA fingerprinting

1986: 1st used to solve a forensic case

How was DNA fingerprinting used in its 1st case?

Helped solve a double rape-murder case

4 ways DNA can be found @ a crime scene

1. Body Fluid

2. Hair roots

3. Marrow (Bones)

4. Sometimes can be pulled from cells left from fingerprints

4 ways to collect/store DNA w/out breaking it down

1. Blood: Collected with sterile cotton swab

2. Body fluids: Collected in borous containers

3. Frozen: Preserve DNA

4. Dried: Prevent decomposition

1st step of DNA Fingerprinting

Cut the DNA with a restriction enzyme

2nd step of DNA Fingerprinting

Copy the DNA with a PCR machine

3rd of DNA Fingerprinting

Separate the DNA with pieces by size with a gel electrophoresis machine

Can DNA evidence always prove someone committed a crime?

No, DNA evidence is reliable for eliminating suspects, but it does not always definitively prove that a specific person committed a crime

CODIS

Combined DNA index system used to enter DNA profiles since it’s a national databank

John Doe Warrant

DNA warrant that keeps the Statue of Limitations from running out on a case. For when investigators have a DNA profile but no suspect. It's useful because it keeps a door open for new potential DNA that could be solved later

3 ways someone can get ur DNA w/out u knowing

1. Trash

2. Bodily fluids

3. Hair root

5-Step Process of DNA Extraction Lab

1. Detergent disrupts cell membrane so it bursts open the cells to release the DNA

2. Proteinase K cuts the histones to free DNA

3. Salt solution is added to the DNA b/c salt causes the proteins to clump together

4. Isopropyl alcohol is added so DNA comes out of solution, allowing it to be seen by the naked eye

5. DNA will then be frozen

What DNA fingerprint looks like

Moral issues brought up about collection of DNA and what do u think of them

It’s kinda weird to have everyone’s DNA but I firmly believe in collecting DNA from people with criminal records

3 reasons for DNA Extraction

1. Genetic testing

2. Body identification

3. Analysis of forensic evidence