17. Can you extract human DNA using this protocol?

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). This is because you're not likely starting the protocol with the required amount—1/2 cup—of human cells! 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.

18. What can be done with my extracted DNA?

This sample could be used for gel electrophoresis, for example, but all you will see is a smear. The DNA you have extracted is genomic, meaning that you have the entire collection of DNA from each cell. Unless you cut the DNA with restriction enzymes, it is too long and stringy to move through the pores of the gel.

A scientist with a lab purified sample of genomic DNA might also try to sequence it or use it to perform a PCR reaction. But, your sample is likely not pure enough for these experiments to really work.

19. How is DNA extraction useful to scientists? When do they use such a protocol, and why is it important?

The extraction of DNA from a cell is often a first step for scientists who need to obtain and study a gene. The total cell DNA is used as a pattern to make copies (called clones) of a particular gene. These copies can then be separated away from the total cell DNA, and used to study the function of that individual gene.

Once the gene has been studied, genomic DNA taken from a person might be used to diagnose him or her with a genetic disease. Alternatively, genomic DNA might be used to mass produce a gene or protein important for treating a disease. This last application requires techniques that are referred to as recombinant DNA technology or genetic engineering.

20. Can I use a microscope to see the DNA that I extract?

Unfortunately, a microscope will not allow you to see the double helical structure of the DNA molecule. You'll only see a massive mess of many, many DNA molecules clumped together. In fact, the width of the DNA double helix is approximately one billionth of a meter! This is much too small to see, even with the most powerful microscope. Instead, a technique called X-ray crystallography can be used to produce a picture of the DNA molecule. It was by looking at such a picture (taken by Rosalind Franklin) that James Watson and Francis Crick were able to figure out what the DNA molecule looks like.