Nucleic acid isolation

Nucleic acid isolation consists of the extraction of DNA or RNA (or both) from the cells. Sources of DNA are white blood cells in a blood sample (red blood cells do not have a nucleus; therefore do not contain DNA), saliva, hair follicles, sperm heads, muscle tissue, bones or teeth. With regards to RNA, there are many types of RNA molecules in a cell. When isolating RNA from a tissue sample all types of RNA (= total RNA) are isolated.

There are different protocols that can be followed for nucleic acid isolation, but the general steps are:

• 1) Nucleic acid extraction (lysis and isolation)
• 2) Nucleic acid purification
• 3) Quantification and purity analysis.

When working with nucleic acids it is very important to protect the sample from contamination and degradation by RNAses and DNAses. RNAses in particular are very abundant in the environment, which can degrade the RNAs in your sample. Therefore, tissue is usually frozen in liquid nitrogen with a temperature of -196°C minus 196 degrees celsius (boiling temperature of liquid nitrogen). At this low temperature, the enzymes become inactivated and all biological functions stop.

After isolating the nucleic acids you can use sequence isolation techniques to isolate specific sequences of your DNA or RNA.

Nucleic acid isolation methods

• Phenol-chloroform method

• Guanidium thiocyanate-phenol-chloroform extraction

• Plasmid extraction with miniprep

• Gel extraction after size separation