Introduction
-Deoxyribonucleic acid (DNA) is a nucleic acid that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses.
-Nucleic acids are biopolymers formed by simple units called nucleotides. Each nucleotide is composed of a nitrogen-containing nucleobase (G, T, C, A) as well as a monosaccharide and a phospate group.
-These nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next.
Materials
- 1L Erlenmeyer flask
- 100mL beaker
- 10mL graduated cylinder
- Small funnel
- Glass stirring rod
- 10mL Pipet
- Knife
- Safety goggles
- Cheesecloth
- Kiwi
- Banana
- Pineapple juice (1mL / 5mL)
- Distilled Water
- 90% Ethanol ice-cold
- 7mL DNA buffer
50mL dish soap
15g NaCl
900mL tap water
Objectives
- Study the DNA structure
- Understand the process of extracting DNA from a tissue
Procedure
Put the ethanol in the freezer, we will need it really cold later.
- Prepare the buffer in a 0'5L beaker: Add 450mL of tap water, 25mL of a dish soap and 7g NaCl. Stir the mixture.
1. Peel the kiwi/banana and chop it to small pieces. Place the pieces of the kiwi in one 600mL beaker and smash with a fork until it becomes a juice puree.
2. Add 8mL of buffer to the beaker.
3. Later mash the kiwi/banana puree carefully for 1 minute without creating many bubbles.
4. Finally filter the mixture: put the funnel on top of the graduated cylinder. Place the cheesecloth on top of the funnel.
5. Add beaker contain carefully on top of the cheesecloth to fill the graduated cylinder. The juice will drain through the chessecloth but the chucks of kiwi/banana will not pass through into the graduated cylinder.
6. Add the pineapple juice to the green juice (1mL of pineaplle juice to 5mL of DNA solution). This step will help us to obtain a purer solution of DNA.
7. Tilt the graduated cylinder and pour in a equal amount of ethanol witg an automatic pipet. Put the ethanol through the sides of the graduated cylinder very carefully. You will need about equal volumes of DNA solution to ethanol.
(Dania's blog photo)
8. Place the graduated cylinder so that it is eye level. Using the stirring rod, collect DNA at the boundary of ethanol and kiwi/banana juice. Do not stir the kiwi juice; only stir in the above ethanol layer.
9. The DNA precipitate looks like long, white and thin fibers.
10. Gently remove the stirring rod and examine what DNA looks like.
RESULTS
QUESTIONS
1. Like a gelatine, white
2. To brake the cells, it's located in the cell wall
3. We add salt to brake the cells and soap to clean the proteins. Papaine cleans and delete the proteins.
4. It's a good method to catch it because the DNA goes to ethanol.
