DNA Extraction - Topic 3 - Paper 1

Question 1

Give the method for extraction of DNA from fruit

Answer 1

1) Mash up some strawberries with mortar and pestel
2) Place a teaspoon of salt and a small volume of detergent into a beaker
3) **Add the mashed strawberries to the salt and detergent solution and mix well
5) Filter the mixture with filter paper to remove the insoluble parts of the cell and retain only the filtrate
6) Gently add some ice-cold ethanol to the filtrate
7) Gently remove stringy white DNA precipitate from solution with a glass rod

Question 2

What does the detergent do in DNA extraction?

Answer 2

Break down cell membranes to release DNA

Question 3

What does the salt do in DNA extraction?

Answer 3

Make the DNA stick together

Question 4

Name the two components of the initial solution in the beaker for DNA extraction

Answer 4

Detergent - break down cell membranes ro release DNA
Salt - clump DNA together

Question 5

Is DNA soluble in cold alcohol?

Answer 5

No

Question 6

Describe the precipitate DNA forms when placed in ice-cold ethanol

Answer 6

Stringy white precipitate

Question 7

How would you remove the DNA’s white precipitate from the final solution?

Answer 7

Carefully with a glass rod

Question 8

Describe the liquid that must be added to the DNA solution after filtering out insoluble parts of the fruit cells in DNA extraction

Answer 8

Ice-cold ethanol

DNA is insoluble in ice-cold alcohol so a white precipitate will be formed, which can then be removed carefully with a glass rod