We are living in the post-Human Genome Project age, and you could take a sample of your own DNA, mail it into a lab, and receive a report on all the different genetic risk factors you carry, and also see your own genome sequence. So, is this a helpful thing? Should you spend the money?
First, a mini introduction to DNA. DNA stands for deoxyribonucleic acid, and consists of 4 different molecules: A, G, T, and C. The order of A,G,T, and C forms a "code" which tells your cells how to make proteins, function, cooperate with each other, and otherwise "live." Certain stretches of DNA contain your genes. If you were to stretch out the DNA inside a single one of your cells, it would be about 2 meters (2.19 yards) long! Because it is so long and must fit inside a tiny cell's nucleus, DNA is wrapped up and packaged very tightly. DNA is wound up around histones (a group of proteins), then folded up, and folded up again into chromosomes. In order for your cell to "read" your DNA, it must first unwind it, and then use various enzymes and cofactors to decode it. Think of your DNA as a book of instructions on how to make a person. The enzymes and cofactors are the "readers" of the book, and different types of cells in your body will use different chapters of the same book (How to Be a Nerve Cell or How to Be a Skin Cell). Both the content of the book (your genome) and the readers (context, cell type, environment) are very important. So, how about sequencing your own DNA?
This is important if your family carries certain genetic diseases, such as Huntington's disease, cystic fibrosis, the BRCA1/BRCA2 mutations that cause familial breast cancer, or other well-known genetic diseases. Your doctor or a genetic counselor can explain your specific family risks based on your family's history. In most cases, it is not that simple though. A set of 10 genes might determine your risk for diabetes, for example, and environment also plays a big role. Most of your traits are based on multiple, many genes and your environment, and it just isn't as simple as sequencing your DNA. Plus, we are still learning things about DNA. Your actual protein coding genes only take up about 1-2% of your genome. We used to call the rest "junk DNA," but turns out we just didn't know what it was for. Now we know that some of the "junk" DNA codes for small RNAs and other factors that regulate our own genes (coding for the "readers," folks). Plus, some of this extra DNA contains regulatory regions and other important stuff. We are still learning about our genomes, so some of your genome sequence is still a mystery as to what it means.
We are moving towards a system of "personalized medicine." For example, it is known that certain genes determine whether a certain drug will help you or not. This is useful for cancer and other diseases where there are multiple drugs available, and the doctor needs to choose the best one for you.
The movie GATTACA came out just when the human genome was first being sequenced, and at the time it seemed like we might be able to take a child's DNA at birth and determine everything about them. But now, we know that DNA is very important, but it is just the beginning of who we are. We can already affect our DNA "readers" through our lifestyles and habits, and someday we can probably edit our own books (that is gene therapy, folks).