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What Is DNA Precipitation?

DNA precipitation is a crucial laboratory technique used to isolate DNA by converting it from a solution into a solid form. This process involves adding alcohol and salt to separate pure DNA strands from other cellular components. It's like fishing for the essence of life in a molecular sea. Curious about how this technique unlocks the secrets of genetics? Let's dive deeper.
Jillian O Keeffe
Jillian O Keeffe

Deoxyribonucleic acid (DNA) precipitation is a key step in the isolation and purification of genetic material in science. Generally, a sample of biological tissue contains DNA or RNA along with the rest of the organism body.To test the DNA, a scientist has to separate out the DNA from all the other substances. DNA precipitation refers specifically to a step that involves the separation of dissolved DNA from the liquid it is dissolved in. Common methods of DNA precipitation include addition of ethanol, ispropanol or glycogen to the liquid, which makes the DNA solidify in lumps and fall to the bottom of the liquid sample.

Initial steps in the purification of DNA from a sample can be as simple as crushing up leaves in a bowl to break down some of the structure. Then the mash can be broken down with chemicals or enzymes that leave the DNA intact. Commonly, geneticists use a centrifuge to help split up different components of a sample. This is a machine that spins a sample so that the heaviest component sinks to the bottom, and the lightest rises to the top.

Geneticists often use a centrifuge to split different components of a DNA sample.
Geneticists often use a centrifuge to split different components of a DNA sample.

By removing various unwanted components, the geneticist is commonly left with a clear liquid that contains the genetic material. He or she then needs to take out the DNA dissolved in that liquid, and discard the liquid and the other substances in the liquid. DNA precipitation is the way in which this is achieved. Most often, the scientist needs to add a chemical to the liquid perform DNA precipitation.

DNA precipitation allows scientists to isolate and purify genetic material.
DNA precipitation allows scientists to isolate and purify genetic material.

Ethanol or isopropanol, which are both forms of alcohol and fall into the solvent group of chemicals, are the most common chemicals used for DNA precipitation. Glycogen is another substance that can precipitate DNA, but it is less commonly used, apart from precipitating low concentrations of genetic material. When these chemicals mix with dissolved DNA, their chemistry allows them to alter the way DNA fits into its environment. Whereas before, the DNA mixed easily with the liquid, after the chemical addition, it stops bonding with the liquid and instead forms into a solid.

Ethanol and isopropanal are often used for DNA precipitation.
Ethanol and isopropanal are often used for DNA precipitation.

This solid is normally whitish and clumps together. As some of the solid is still in small particles, however, the scientist usually places the sample into a centrifuge to spin all the solids together into a pellet at the bottom of the sample tube. This is the purified form of the DNA originally present in the sample, which is useful for testing. Generally, the liquid the pellet is suspended in is removed from the tube, and the pellet may also be dried to allow the chemicals to evaporate off, in order to render the pellet as pure as possible.

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    • Geneticists often use a centrifuge to split different components of a DNA sample.
      By: Monkey Business
      Geneticists often use a centrifuge to split different components of a DNA sample.
    • DNA precipitation allows scientists to isolate and purify genetic material.
      By: Darren Baker
      DNA precipitation allows scientists to isolate and purify genetic material.
    • Ethanol and isopropanal are often used for DNA precipitation.
      By: adimas
      Ethanol and isopropanal are often used for DNA precipitation.
    • DNA must be separated from other substances for testing.
      By: Ragne Kabanova
      DNA must be separated from other substances for testing.