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DNA EXTRACTION LAB

Genetic Science Learning Center

http://gscl.genetics.utah.edu/wheatgerm/

Dna replication

Materials Needed

      Raw wheat germ - 1 gram or 1 teaspoon.

      Liquid detergent - 1 ml or 1/4 teaspoon

      Alcohol - 14 ml or 1 tablespoon

      50-60ー Celsius tap water - 20 ml or 1 tablespoon
      Do not use water hotter than 50-60ー C.

      50 ml beakers

      Graduated cylinder

      Wooden applicator stick

      Eyedropper

 

Extracted DNA

Procedure

 

What is DNA?

DNA is the abbreviation for deoxyribonucleic acid.

DNA is found in the nucleus of every cell & it stores the information that makes up living organisms

 It is a double helix of 4 nucleotides. It contains a code hat allows the body to make up proteins.

The nucleotides are

CYTOSINE

GUANINE

ADENINE

THYMINE

 

DNA

When forming the double helix the nucleotides will only bind this way

CYTOSINE-GUANINE

GUANINE-CYTOSINE

ADENINE-THYMINE

THYMINE-ADENINE

 

Why use wheat germ?

 

Wheat germ comes from wheat seeds. The "germ" is the embryo, which is the part of the seed that can grow into a new wheat plant.

 

What does the detergent do?

Detergent cleans dishes by removing fats. It acts the same way in the DNA extraction protocol, pulling apart the fats (lipids) and proteins that make up the membranes surrounding the cell and nucleus. Once these membranes are broken apart, the DNA is released from the cell.

Soap molecules and grease molecules are made of two parts:

Both soap and grease molecules organize themselves in bubbles (spheres) with heads outside to face the water and tails inside to hide from the water.\

soap and grease

 

When soap comes close to grease, it captures it, forming a greasy soapy ball.

A cell's membranes have two layers of lipid (fat) molecules with proteins going through them.

cell membrane

 

When detergent comes close to the cell, it captures the lipids and proteins and releases the DNA.

Cell membrane and detergent

 

What does the alcohol?

The DNA released from the cell nucleus is dissolved in the water/detergent/wheat germ solution and cannot be seen. DNA precipitates (separates) out of solution in alcohol, where it can be seen. Besides allowing us to see the DNA, the alcohol separates the DNA from the other cell components, which are left behind in the water solution

What does the warm water do?

It also inactivates (denatures) the deoxyribonuclease enzymes (DNase) which, if present, would cut the DNA into such small fragments that it would not be visible.

Enzymes are proteins which help chemical reactions in the body speed up.

Denatured enzymes and DNA unravel, loose their shape, and thus become inactive. Enzymes denature at 60ー Celsius, and DNA denatures at 80ー Celsius.

 

 

DNA Graphic from library.thinkquest.org/27893/data/dna.html