Isolation of Nucleic Acids

Question 1

Lysis, precipitation and purification

Answer 1

Lysis breaks open a cell to expose its internal components, while precipitation and purification remove waste materials and allow a high concentration of DNA to be collected

Question 2

Phenol chloroform

Answer 2

Cells are lysed, and an equal volume of phenol:chloroform is added - then the sample is centrifuged. This allows layers to form in the Eppindorf tube - DNA/RNA, protein, waste materials (lipids) - so DNA can be easily extracted. This process can be repeated to achieve a higher concentration of DNA

Question 3

Spin columns

Answer 3

Cells are lysed and ethanol/buffer is added - then the sample is centrifuged. DNA binds to silica discs by the formation of salt bridges due to a high Na+ concentration. Waste material slips through the discs. Pure DNA can be eluted from the silica discs by adding elution buffer

Question 4

Ethanol precipitation

Answer 4

Cells are lysed, and centrifuged. Ethanol and sodium acetate are added, which disrupts the polar phosphate backbone of DNA due to a high Na+ concentration - so it can’t dissolve in water allowing a high concentration of DNA to precipitate. Further washing with ethanol will remove salt, creating purer DNA