Extracting DNA

Question 1

1. Why do we dissolve salts in sample

Answer 1

The + sodium ions in the salt shield the - phosphate groups of the DNA which helps them precipitate out

Question 2

2. Why do we add detergent

Answer 2

To dissolve nuclear membrane and phospholipid bilayer by attracting them away from their structure

Question 3

4. Why do we stand the beaker in a water bath at 60 degrees for exactly 15 minutes

Answer 3

To degrade membrane phospholipids releasing the DNA
60 is high enough To denature enzymes which would cut DNA into fragment
If it’s longer than 15 minutes DNA would break down

Question 4

5. Why do we cool the mixture in an ice bath

Answer 4

This slows down the breakdown of DNA which would occur if higher temperatures were maintained And makes it harder for us to see

Question 5

6. Why do we blend the mixture on high speed For only 5 seconds

Answer 5

This degrades the cell wall and cell membrane faster releasing DNA, But if we blend for too long it would break the DNA making it harder for us to see

Question 6

7. What do we get when we filter the mixture

Answer 6

The filtrate contains DNA and protein histones that its ravelled around

Question 7

8. Why do we add protease

Answer 7

To degrade the histones proteins by Hydrolysing peptide bonds

Question 8

9. Why do we pour ice cold ethanol on top

Answer 8

Negative charge phosphate groups with DNA are surrounded by water molecules, ethanol and Sodium ions from the salt disrupt these interactions making Nucleic acid insoluble in cold ethanol and precipitate out. The DNA is seen as a white material

Question 9

Why would we crush the cell before adding detergent

Answer 9

To separate and break open cell walls if we are using plant cells or multicellular organisms