DNA Extraction of a Wheat Germ.

Question

So, our class did a DNA extraction of a wheat germ. From this lab I learned that putting warm water in to the wheat germ allows the fats in the membrane that surround the cells and the nucleus, to soften. The warm water will also denature enzymes that may damage the DNA. The warmth will also enhance the action of the liquid soap when it is added. Also when the liquid soap is added it breaks up the phospholipid cell walls even more, the cell membranes, and nuclear membranes. The liquid soap removes fats and proteins by pulling them apart and this will allow the nucleus to open to which will release DNA. Then by adding ethanol to this mixture it causes the DNA to precipitate because the positive ions in the ethanol were attracted to the negatively charged DNA. Also the ethanol will dehydrate and precipitate the DNA, as the DNA is insoluble in ethanol. This will allow the DNA to precipitate. 

 

QUESTION: How would the process or the results be different if I were to use a vegetable, animal cell, or a type of fruit? Explain. 

Answer 1

Shreya,

 

Animal cells are different than plant cells; they lack cell wall present in plant cells. The general protocol of DNA isolation includes:

 

1. Breaking down of proteins

 

2. Digesting proteins by Proteinase such as proteinase-K for denaturation and easy removal

 

3. Removal of proteins and cell-debris by phenol-chloroform extraction  or running through columns

 

4. Precipitation by ethanol and salt, followed by 70% ethanol wash.

 

 

Different animal and plant cells have different membranes/walls and they differ in protein structure. Therefore, sometimes heat or sometimes enzymatic treatment is necessary for protein breakdown. The time and treatment differs based on complexity of protein in the tissue/organism in  question.

 

Soap is not used for animal tissues and cells. In general, nuclear membrane is easier to break down in comparison to cell membrane.

 

Hope this helps.