Forensic Investigation Bone/DNA Detectives

What else can we do? We now have a description of the individual that the bones belong to, but there are 2 missing persons that fit this description Blood typing, dental records, or DNA Fingerprinting could all help narrow this down.

What is DNA? Deoxyribonucleic acid- biomolecule made of nucleotide subunits DNA is found in bodily fluids, living tissues, hair, and BONE Humans only have 0.1% of their DNA that is different, but that is 3 million base pairs

PCR Once we get the small amounts of DNA from the bone and missing persons, it needs to be amplified Polymerase Chain Reaction is a process that uses a thermocycler machine and the polymerase enzyme to make many copies of DNA in a short amount of time

Restriction Enzymes Enzymes are proteins that speed up chemical reactions Restriction enzymes catalyze the reaction of breaking DNA into smaller fragments These fragments (RFLP’s) are different sizes for different individuals because of the 3 million BP that are different

Restriction Enzymes: Molecular Scissors Restriction enzymes (endonuleases) cut DNA at specific sequences What kinds of bonds are broken when restriction enzymes cut? Covalent bonds (within a single strand) Hydrogen bonds (between strands) as a result of the strands coming apart Hydrogen bond Covalent bond

Origins of Restriction Enzymes Naturally found in different types of bacteria (prokaryotes) Bacteria use restriction enzymes to protect themselves from foreign DNA Bacteria have mechanisms to protect themselves from the actions of their own restriction enzymes Have been isolated and sold for use in lab work

Examples of Restriction Enzymes Organism source Recognized Sequence EcoRI Escherichia coli 5' GAATTC 3’ 3' CTTAAG 5’ TaqI Thermus aquaticus 5' TCGA 3’ 3' AGCT 5’ HindIII Haemophilus influenzae 5'AAGCTT 3’ 3'TTCGAA 5’ BamHI Bacillus amyloliquefaciens 5' GGATCC 3’ 3' CCTAGG 5’ AluI Arthrobacter luteus 5' AGCT 3’ 3' TCGA 5’ Bases in blue are the actual bases that restriction enzymes cut between. In many cases, there are multiple subunits of a restriction enzyme– each subunit recognizes a particular sequence on one of the strands then cuts it at a certain distance away from that. Recognized sequences for restriction enzymes tend to be palindromic (read the same backwards and forwards)

Electrophoresis DNA is too small to see with the naked eye DNA is loaded into an agarose (sugar) gel We use electrophoresis (movement due to an electrical current) to separate the different size DNA fragments DNA has a negative charge (phosphate groups) and is repelled by the negative side of the apparatus and attracted to the positive side (like repels, opposites attract)

Smaller pieces of DNA move faster (further) because they have less frictional resistance in the agarose.

Uses Can be used for crime scene to match suspect and crime scene DNA Can be used in paternity cases to match baby with possible fathers Can be used in forensic analysis to match bone DNA with missing person DNA