CHAPTER 13 DNA: The Indispensable Forensic Science Tool Cameron Waldron Forensics

What is DNA DNA= Deoxyribonucleic acid Parts of DNA The molecules carry the body’s genetic information Parts of DNA Chromosomes- strands of genetic material Genes- arranged along the chromosomes like beads on a thread

DNA at Work Traits controlled by DNA come from proteins. A protein comes from a link of amino acids (the building blocks of proteins) There are 23 pairs of chromosomes

Replication of DNA It begins with the unwinding of the strands in the double helix PCR (polymerase chain reaction) Pieces of DNA can be copied with the aid of a DNA polymerase

Recombinant DNA: Cutting and Splicing DNA Genetic code- the relationship between the base letters on a DNA strand and the type of protein specified for manufacture by the sequence of these letters Restriction enzymes- chemicals that act as scissors to cut DNA molecules at specific locations

DNA Typing Restriction Fragment Length Polymorphisms Tandem Repeats- region of a chromosome that contains multiple copies of a core DNA sequence that are arranged in a repeating fashion Restriction Fragment Length Polymorphisms (RFLPs)- repeat segments cut out of the DNA double helix by a restriction enzyme

DNA RFLP process DNA is cut into fragments Fragments are separated into bands by electrophoresis DNA band pattern is transferred to a nylon membrane Membrane with DNA fragments positioned exactly Radioactive DNA probe is added X-ray film placed next to the membrane to detect the pattern Developed X-ray film showing DNA fragment that combined with radioactive probe

Polymerase Chain Reaction Primer- short strand of DNA used to target a region of DNA for replication by PCR Steps of the PCR process Heat the DNA strands to about 94 degrees Add the primers to the separated strands Add the DNA polymerase and a mixture of free nucleotides to the separated strands

Short Tandem Repeats The latest method of DNA typing is STR STRs are locations on the chromosome that contain short sequence elements that repeat themselves within the DNA molecule Multiplexing- simultaneously detects more than one DNA marker in a single analysis

Mitochondrial DNA Mitochondria are cell structures found in all of our cells Sequencing is a procedure used to determine the order of the base pairs that comprise DNA

Combined DNA Index System (CODIS) CODIS is a computer software program developed by the FBI It lets crime labs to compare DNA profiles electronically

Collection and Preservation of Biological Evidence for DNA Analysis Picogram- one trillionth of a gram Low Copy Number- fewer than 36 DNA bearing cells Epithelial Cells- The outer layer of skin cells Substrate Control- An unstained object adjacent to an area upon which biological material has been deposited