Dynamic DNA Explained

Deoxyribonucleic Acid

What is it? 
We're sure you've heard of this term; Deoxyribonucleic Acid. No? How about DNA? Well good news, they are the same! DNA is the shortened way of saying the long molecule's name. DNA is known for its double helix shape.
DNA is made up of chemical bases, four to be precise, A, T, C, and G.
A: Adenine
T: Thymine
G: Guanine
C: Cytosine
These chemical compounds match up to one another; A to T and C to G.  This connection is called a base pair. There is another compound, Uracil, that can attach to Adenine, but this is a result of RNA, not DNA.

Double Helix / A-T and G-C pairing

So what is RNA?
We are glad you asked! RNA (Ribonucleic acid) is similar to DNA. They are both nucleic acids but they do different things. DNA is complex and holds secret messages in its makeup. (It's like a chemical spy holding all the secrets about you!) RNA is the only one who can understand these secrets. RNA, in a sense, translates these messages for proteins and other things; it transcribes the message DNA has.

DNA and RNA are also different in shape. Like we said, DNA has a double helix shape; this shape is like a spiral staircase. RNA however is single stranded. RNA has a a couple different shapes, depending on how its base pairs match up.

Shape of RNA/ C-G and A-U pairing

Where is DNA found?
DNA is found inside the nucleus of the cell. The nucleus is a great place for a nucleic acid! The nucleus is inside the cellular membrane of the cell though. How do we break open the microscopic cell membrane and the nucleus? Dish soap! The dish soap breaks apart the molecules of the cell. Both dish soap and the cell membrane have hydrophobic (scared of water) and hydrophilic (loves water) sides.

Why add contact solution, pineapple juice or meat tenderizer?
DNA is folded and cushioned by protein in the cell. The contact solution is acidic and separates the DNA from the protein.

How come the white stuff is DNA?
The DNA is the white, stringy stuff you see in the top layer of alcohol. Alcohol forms a layer on top of the water because it is less dense. Adding salt to the mixture (at the beginning) helps DNA stick together.  But when in water DNA is dissolved. Adding the alcohol brings the DNA 'out of solution', making it undissolved. This is called precipitation.


Further Information:
http://ghr.nlm.nih.gov/handbook/basics/dna
http://www.usask.ca/education/coursework/mcvittiej/bio30unit1/overheads/1.23.htm

Dynamic DNA

This week we're doing an experiment with DNA! Now doesn't that sound exciting? In this lab you will be able to see the very small DNA from a cheek cell or from inside a pea. The procedures for cheek cells and peas are a little different, so make sure you read the instructions.

Pre-Lab:
If you have access to a microscope we suggest you take a look at the cells in your mouth.
1.) Place a drop of iodine on a microscope slide.
2.) Take a toothpick and gently scrape the inside of your cheek.
3.) Place the toothpick in the iodine and swirl.
4.) Start with low power (4x) and look at your cheek cells!
Now that you have a general idea of what your cheek cells look like try this experiment.

Materials
- Spilt Peas, Strawberries or any other DNA source (if not using cheek cells)
- Blender
- Salt
- Water
- Measuring cups
- Test tubes
- Dish soap
- Contact Solution (meat tenderizer or pineapple juice)
- Rubbing alcohol (isopropyl or ethanol)
- Glass stirring rod (wood skewer or Q-tip)

Procedure:
Cheek Cells
1.) Swish salt water in your mouth for 30 seconds. (This is a long time, but you can do it!)
2.) Spit the water into a cup, then pour it into a large test tube.
3.) Add 1 teaspoon of dish soap to the large test tube.
4.) Gently shake the test tube. (If you do this in a beaker or cup, gently stir the cup)
5.) Pour about 1 teaspoon of alcohol into the tube.

The best way to do this is by tilting the test tube and slowing pouring the alcohol.

Ideally there will be a small layer of alcohol above the soapy mixture.

6.) Using the glass stirring rod - twirl in one direction to collect the DNA

Split Peas & Other Foods:

1.) In a blender add and blend on high for 15 seconds:

- 1/2 cup split peas

- 1/8 teaspoon table salt

- 1 cup water

2.) Pour the pea mixture through a strainer (you want the liquid) and let sit for 5-10 minutes

3.) Pour some of the liquid into a test tube

4.) Add 1 teaspoon dish soap to the large test tube

5.) Add some contact solution to the test tube 

(you don't need a lot, a small squirt or a pinch for tenderizer)

6.) Add about 1 teaspoon of alcohol to the test tube

Just like the cheek cells you want a layer of alcohol above the soapy pea mixture

7.) Using the glass stirring rod - twirl in one direction to collect the DNA

You can save this DNA or look at it on a wet slide under a microscope.

To save: Put the DNA in a small test tube or container with some alcohol.

(Pictures for the steps to come)

Further information:
http://www.middleschoolscience.com/microscope.pdf
http://www.pbs.org/wgbh/nova/teachers/activities/pdf/2809_genome_01.pdf
http://www.pbs.org/wgbh/nova/teachers/activities/2809_genome.html
http://learn.genetics.utah.edu/content/labs/extraction/howto/