DNAThe Code of Life

© 2013 Project Lead The Way, Inc.Medical Detectives

What is DNA?

• DNA (deoxyribonucleic acid) is the genetic material in all known living organisms and some viruses

• It can be carried from one generation to another

The “Code of Life”

• Information in DNA determines an organism’s characteristics

• DNA consists of base pairs Adenine, Thymine, Guanine, and Cytosine

The “Code of Life”

• DNA can be compared to a cookbook with instructions about how to create and maintain a specific living thing.

• Genes can be compared to the individual recipes in the cookbook. They encode the information to make proteins and determine how many of those proteins to make.

Packaging DNA

• The basic structure of DNA is that of a twisted ladder called a double helix.

• To fit into the nucleus, the double helix wraps around proteins called histones.

Packaging DNA• The DNA then

condenses into chromosomes.

• Human beings have 46 chromosomes in the nucleus of almost every cell.

Chromosomes of a human male

DNA Structure

DNA ExtractionStep 1: Collect cheek cells• Sports drink is used as a mouthwash

collection medium.• Sports drinks contain salt in a

concentration similar to the cheek cells; this prevents the cells from breaking open and releasing their DNA before they are collected.

DNA ExtractionStep 2: Cell lysis• The membranes that surround and

protect the cell and nucleus must be broken to release the DNA in a process called cell lysis.

• A detergent-based cell lysis solution will be used to degrade the membranes.

• The remaining solution is known as cell lysate.

DNA ExtractionStep 3: DNA precipitation• The DNA in the cell lysate is in solution

and is not visible (like sugar in water).• DNA is insoluble in ethanol (like sand in

water).• DNA from the cell lysate can be

visualized by applying a layer of ethanol on top of the cell lysate.

Importance of DNA Extraction

• DNA extraction is the first step in many in-depth experiments including:– The study of heredity– Potential treatments of diseases

• Extracted DNA can be used to create DNA fingerprints to help:– Diagnose genetic diseases– Solve criminal cases

Image Resources

By KES47 (File:Chromosome zh.svg) [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia CommonsFree images courtesy of Wikimedia Commons http://commons.wikimedia.org/wiki/Main_Page