Question

Material:

• Plant tissue (strawberries or split peas)
• 400-mL beaker
• Blender
• Table salt
• Tablespoon
• 1/8 teaspoon
• Liquid detergent
• Test tubes and test tube rack
• Meat tenderizer
• Glass rods
• Ice-cold 70–95% ethanol
• Ice-cold dH₂O
• Strainer

Procedure – DNA Extraction

1. Combine in a blender:

• 1/2 cup frozen green split peas or approx. 1/2 cup frozen strawberries
• 1/8 teaspoon table salt
• 1 cup cold (refrigerated or use ice to chill) water

2. Cover and blend on the high setting for 30 seconds.
3. Pour the blended material through a strainer into a 400-mL beaker. Discard the solid material trapped by the strainer into the trash. This step removes the seed coat and the cell walls from the plant cells.
4. Add 2 tablespoons of liquid detergent to your beaker and swirl to mix. Let the mixture stand for approximately 10minutes. Detergents dissolve lipids, such as phospholipids in plasma and nuclear membranes.
5. Obtain a test tube for each member of each of your group.pour the mixture into the test tubes until they are each about 1/3 full.
6. Add a pinch of meat tenderizer to each test tube and stir gently with a glass rod. if you stir. vigorously, you will break the DNA into short strands that are had to see. Meat tenderizer contains enzymes that digest histones, the proteins around which the DNA is wound.
7. Tilt your test tube and slowly pour cold 70-95% ethanol down the side of the tube so it forms a layer on top of the DNA mixture until you have the same volume of alcohol as the DNA mixture.
8. After a few minutes, the DNA will rise into the alcohol layer. DNA forms a whitish layer at the interface between the alcohol and the lower cell debris-containing layer.

1:Why did you add detergent to the homogenized tissue sample?

2:How did you remove the cell walls.

3:Why did you add meat tenderizer to your test tubes?.

4:What are histones

Answer 1

This is the procedure of DNA Etraction from plant tissues.
Here we have taken strawberries or peas tissues whose each cell contain DNA material.
Plant cell contains cell wall made up of cellulose, hemicellulose and pectin.
Cell wall covers the plasma membrane. Inside the cell membrane many cell organalles are present.
At the centre of cell a nucleus is present which is enclosed by nuclear envelop it contains DNA Inside it.

So in order to extract DNA From the plant tissues. First we need to break tissues into cell then need to dissolve cell wall. After dissolving cell wall we should also dissolve nuclear envelope and inside it DNA will be available in coiled sturucture. Histones are the proteins which helps in coiling of DNA.
For extraction of DNA we need uncoiled linear chain of DNA.

1) We are grinding tissues to break them into cells as well as we are adding detergents which dissolves plasma membrane and nuclear membrane and exposes Coiled DNA .

2) Cell walls are broken down by grinding and straining the mixture

3) Then after removing cell wall, plasma membrane and nuclear membrane we need to uncoil DNA as well as we should make it into small strands. For that we added meat tenderizer which contains enzymes which has the capacity to break histone proteins which are repsonsible for DNA coiling and long chain.So meat tenderizer given us uncoiled small DNA strands.

4) Histones are special proteins which you will find in eukaryotic cell DNA.
This proteins helps in coiling as well as giving specific structure to DNA. because of this DNA Exists in Nuclesomes. DNA Strands wraps around this protein and forms nucleosomes and makes itself fit for nucleus.