However, they can be expensive to use routinely, so many labs have their own methods for DNA extraction. The cells in a sample are separated from each other, often by a physical means such as grinding or vortexing , and put into a solution containing salt. The positively charged sodium ions in the salt help protect the negatively charged phosphate groups that run along the backbone of the DNA.
A detergent is then added. The detergent breaks down the lipids in the cell membrane and nuclei. DNA is released as these membranes are disrupted.
This can be done by a variety of methods. They are both proteases, meaning they break apart proteins. Enzymatic cleaning solutions for contact lenses also contain proteases to remove protein build-up. These proteases include Subtilisin A extracted from a bacteria and Pancreatin extracted from the pancreas gland of a hog. How much pineapple juice or contact lens solution should I use to replace the meat tenderizer?
You just need a drop or two, because a little bit of enzyme will go a long way. Enzymes are fast and powerful! DNA precipitates when in the presence of alcohol, which means it doesn't dissolve in alcohol.
This causes the DNA to clump together when there is a lot of it. And, usually, cells contain a lot of it! For example, each cell in the human body contains 46 chromosomes or 46 DNA molecules. If the human body is made of about trillion cells, each of which contains six feet of DNA, our bodies contain more than a billion miles of DNA!
There is a protocol that would allow you to stain nucleic acids, but the chemical used would need to be handled by a teacher or an adult. So, for now, you'll just have to trust that the molecules precipitating in the alcohol are nucleic acids. That's exactly right! The procedure for DNA extraction is really a procedure for nucleic acid extraction.
Your DNA may last for years if you store it in alcohol in a tightly-sealed container. If it disappears it's likely because enzymes are still present that are breaking apart the DNA in your sample. Using more sophisticated chemicals in a lab, it is possible to obtain a sample of DNA that is very pure. DNA purified in this way is actually quite stable and will remain intact for months or years. Cells with more chromosomes contain relatively more DNA, but the difference will not likely be noticeable to the eye.
For example, plant seeds yield a lot of DNA because they have very little water in the cell cytoplasm. That is, they have a small volume. So the DNA is relatively concentrated.
You don't have to use very many seeds to get a lot of DNA! Peas are a good source of DNA because they are a seed. But, we also chose the pea for historical reasons. Gregor Mendel, the father of genetics, did his first experiments with the pea plant. How does the experiment compare when using animal cells instead of plant cells?
The DNA molecule is structurally the same in all living things, including plants and animals. That being said, the product obtained from this extraction protocol may look slightly different depending on whether it was extracted from a plant or an animal. For example, you may have more contaminants proteins, carbohydrates causing the DNA to appear less string-like, or the amount of DNA that precipitates may vary. Good sources for animal cells include chicken liver, calf thymus, meats and eggs from chicken or fish.
We at the GSLC have done a fair amount of testing with the split pea protocol and the wheat germ protocol. We have found no difference in the "product" nucleic acids that is observable, whether using meat tenderizer or not. So, the step was left out of the wheat germ protocol, but kept in the split pea protocol just for fun. Even though it's not necessary, it may be doing something we can't see.
For example, perhaps by using the meat tenderizer you get a purer sample of DNA, with less protein contaminating the sample. Yes, in theory. The same basic materials are required, but the protocol would need to be scaled down using smaller volumes of water, soap and alcohol.
That means that you will not extract an amount of DNA large enough to visualize with the naked eye. If you wanted to see it, you would need a centrifuge to spin down to the bottom of the tube the small amount of DNA present in the sample. This sample could be used for gel electrophoresis, for example, but all you will see is a smear.
Unless you cut the DNA with restriction enzymes, it is too long and stringy to move through the pores of the gel. Such changes have both sped up production and increased the yield of DNA. The ability to extract DNA is of primary importance to studying the genetic causes of disease and for the development of diagnostics and drugs. It is also essential for carrying out forensic science, sequencing genomes, detecting bacteria and viruses in the environment and for determining paternity.
Respond to or comment on this page on our feeds on Facebook , Instagram or Twitter. Facebook Twitter Donate to WiB. Importance The extraction of DNA is pivotal to biotechnology. Author Profile. Show caption. What is DNA Extraction? What is it used for? Extraction of DNA is often an early step in many diagnostic processes used to detect bacteria and viruses in the environment as well as diagnosing disease and genetic disorders. Sequencing: Portions of, or whole genomes may be sequenced as well as extra chromosomal elements for comparison with existing sequence in the public data base.
Vortexing with phenol sometimes heated is often effective for breaking down protienacious cellular walls or viral capsids.
0コメント