DNA EVIDENCE

What is DNA? DNA stands for deoxyribonucleic acid and contains genetic information. DNA is a polymer composed of building blocks called Nucleotides. Each nucleotide has three parts. Nucleotides are arranged in a double helix structure with the bases in the middle of the “twisted ladder” There are 4 possible nitrogenous bases in DNA. The are Adenine (A), Thymine (T), Guanine (G) Cytosine (C),

Nuclear DNA vs Mitochondrial DNA Nuclear DNA: -Found in nucleus of every cell in chromosomes. -Codes for traits (genes) are in the base sequences -Areas of “junk DNA” are UNIQUE to each individual and are used for DNA fingerprinting. Mitochondrial DNA: -found in the mitochondria of all cells. - every person’s mDNA is exactly the same as every person in their maternal lineage.

DNA Fingerprinting (NOT FINGER FINGERPRINTS) Common uses: -proving guilt or innocence of a suspect -identifying remains -paternity testing Common sources of DNA associated with forensic investigations: (only need 1 cell) blood, semen, saliva Note: DNA can sometimes be found in a FINGER fingerprint if skin cells were left with the fingerprint.

Electrophoresis: -technique used to analyze molecules -used for DNA analysis and analysis of amino acids in proteins Molecules are placed in a “gel” and an electric current is applied to the gel. Molecules move through the gel due to their attraction to the opposite charge in the gel. Smaller molecules move farther. The gel is then stained to make the molecules visible and the gel is photographed creating a “fingerprint” of the molecules. - In DNA electrophoresis a DNA “fingerprint” is created which consists of bands or patterns of DNA unique to each individual.

We have a mystery to solve!! Go to this website & follow the instructions to create a DNA fingerprint & see if you can solve the mystery!

What factors affect DNA evidence? Several factors can affect the DNA left at a crime scene, such as environmental factors (e.g., heat, sunlight, moisture, bacteria, and mold). Therefore, not all DNA evidence will result in a usable DNA profile. Further, DNA testing cannot identify when the suspect was at the crime scene or for how long. DNA information : CODIS stands for COmbined DNA Index System, which is an electronic database of DNA profiles that can identify suspects. DNA profiles from individuals convicted of certain crimes, such as rape, murder, and child abuse, are entered into CODIS and help officers identify possible suspects when no prior suspect existed. What is CODIS? Did you know? Each human cell contains three billion DNA base pairs. Our unique DNA amounts to 0.1% or 3 million base pairs.

THE INNOCENCE PROJECT The Innocence Project is a national litigation and public policy organization dedicated to exonerating wrongfully convicted individuals through DNA testing and reforming the criminal justice system to prevent future injustice. Local Case: Steven Barnes PCR: Polymerase Chain Reaction: amplifying the amount of DNA (making copies so there is enough to analyze.

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