DNA contains the genetic instructions that determine an organism's characteristics. It can be passed down from parents to offspring. DNA has a double helix structure and is packaged into chromosomes within the nucleus of cells. The basic units of DNA are nucleotides containing combinations of four bases - adenine, thymine, guanine and cytosine. Genes within DNA act as recipes that encode instructions for making proteins. Extracting DNA from cells is the first step for experiments studying heredity and diseases, as well as for DNA fingerprinting used in criminal investigations.

1. DNA
The Code of Life
© 2013 Project Lead The Way, Inc.Medical Detectives

2. 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

3. The “Code of Life”
• Information in DNA
determines an organism’s
characteristics
• DNA consists of base pairs
Adenine, Thymine, Guanine,
and Cytosine

4. 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.

5. 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.

6. 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

7. DNA Structure

8. DNA Extraction
Step 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.

9. DNA Extraction
Step 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.

10. DNA Extraction
Step 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.

11. 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

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