Forensic DNA Analysis Introduction to DNA

The Cell Smallest unit of life Compose all living things The “nucleus” (one of many organelles) contains genetic information the cell needs to exist and reproduce - most cells organize genetic information into chromosomes

Chromosomes our body’s way of organizing all the information that our genetic material contains 23 pairs in humans - each pair contains one from mother and one from father

Genes Each chromosome contains 100s to 1000s of information blocks called genes Each gene is the blueprint for a specific protein in the body - may tell our body what color our eyes are supposed to be, dozens of proteins are responsible for synthesis of ATP, digesting food, etc, etc etc

DNA Each chromosome and every gene is made of deoxyribonucleic acid (DNA) DNA is a polymer of repeating units called nucleotides Each nucleotide contains three parts - phosphate group - sugar (deoxyribose) - nitrogenous base

The nitrogenous base is always one of four molecules: Nucleotides Phosphate Sugar The nitrogenous base is always one of four molecules: adenine guanine cytosine thymine

The DNA Backbone Nucleotides are liked together with alternating P-S-P-S-P……..

The DNA Double Helix DNA is normally double stranded The two nucleotide chains are held together by hydrogen bonds A always pairs with a T on the other strand; C always pairs with G

The DNA Double Helix The two strands wrap around each other to form helical structure shown (double helix)

Functions of DNA Two Types of DNA Two primary functions - transmit information from one generation to the next - provide blueprint for making proteins the same way every time Two Types of DNA nuclear or chromosomal DNA (inherited from mother and father) mitochondrial DNA (inherited from mother only)

DNA Replication DNA is unwound An enzyme called DNA Polymerase adds complementary bases to “single stranded” - A with T - C with G

Restriction Enzymes Enzyme that cuts DNA at specific sequences Recognize and binds to 6-8 nucleotide stretch

Gel Electrophoresis Gel with different sized pores agarose and acrylamide are common materials Load DNA samples into wells at top of gel Run electric current through the gel DNA moves due to negative charge Smaller bands run “faster”