The DNA in every cell in our bodies is in a dynamic state, meaning it is never just sitting around doing nothing. DNA serves as a 'storage unit' for our genetic information (needed to pass on to daughter cells and future generations), as well as the 'instruction book' for making proteins our cells and bodies need for daily bodily functions. For more background on DNA, check out the post 'Basics of DNA', and let me know if you have any questions.
Here I wanted to tell you a little more detail about how DNA accomplishes these two seemingly unrelated tasks. this is part of a series I am posting on the wonders of DNA. In the future I would like to write about the discovery of the double helix, genome sequences and other DNA related topics, so let me know if there is something in particular you would like a better understanding of and I can work it in!
DNA is the molecule that is passed on to the next generation. Your DNA is in your egg or sperm cells (depending on if you are a man or woman). When the egg and sperm unite, the resulting fertilized egg has a copy of the mom's DNA and dad's DNA. As this egg cell divides, forming multiple cells that make up the embryo, this DNA is copied so each cell will have its own copy of the complete DNA set given from mom and dad. This copying process is known as replication. It is a very complicated process that occurs millions of times over the course of embryonic development and beyond (through adulthood). Not only is the process itself complicated, but the timing is complex, as it must be carefully regulated to coordinate with cell division.
Basically, what is happening in replication is that a single cell with a set of DNA is preparing to divide. One thing it must accomplish is to make an extra set of DNA. Once the cell divides, it will form two individual cells (called daughter cells); each of these cells needs its own copy of DNA after the split. Replication of the original DNA accomplishes this task.
Remember the structure of DNA and binding rules (A to T and C to G) as we go through the basics of replication. The picture below from "coolschool" illustrates the basic idea of replication. In step 1 (unzipping), the double helix structure must first be unwound so that each strand of DNA is opened and accessable. In step 2, proteins will come to the site and use each single strand to build a new double strand using the rules of base pairing. In step 3, the completed DNA strands are shown in helical form again (one for each daughter cell).
Imagine if you build a ladder with different color pieces for each step. If you wanted to make another ladder identical to that, you can cut your ladder down the center, and use the binding rules to build up the other half of each of your ladders.
As stated above, DNA is used as the storage unit for passing genetic information on to new cells and new generations. The purpose for this passing on of information is because the function of DNA is to provide the 'recipes' for making proteins needed by the body to perform just about every function you can imagine. So when the DNA is passed on to each generation, it is providing the recipe for making proteins to keep the body working. This is VERY important. Without DNA you wouldn't be here and you wouldn't be able to do anything. Proteins are the basis for all functions in all organisms on Earth - plants, animals, bacteria, etc.
The method of making proteins from DNA is actually a two step process, called transcription and translation. These processes occur independent of replication. Actually transcription and translation are happening just about all the time in every cell of the body. The first step, transcription, involves unwinding a specific section of DNA; the section unwound will be wherever the gene needed happens to be. Once it is unwound a bit, proteins come to the site and use the binding rules similar to replication. The difference is that this time the result isn't another long double-DNA strand, but rather a short single-DNA strand called RNA. RNA will be a copy of one gene only, and they are quite small (relative to gigantic DNA strands).
Once the RNA strand is made, the process of translation begins. While transcription makes RNA from DNA, translation makes protein from the RNA. In order to do this, more proteins come to the RNA piece, and use a different set of rules, the Genetic Code to determine how to make the protein. On the RNA strand, the proteins read 3 bases at a time. Each set of 3 bases has a corresponding amino acid that will be placed in a long chain. This long chain is then folded up and the final product is a protein.
If you would like to visual these three processes, here are some great videos from Youtube. Don't try to figure out the detail they are presenting (unless you want to), but for the basics, just focus on the great animations.
Replication video from "freesciencelectures"
Transcription video from "ndsuvirtualcell"
Translation video from "ndsuvirtualcell"
Don't worry if it sounds complex, it IS complex! Even as complex as this simple explanation sounds, there are so many more levels of complexity. Scientists, specifically molecular biologists, research and use this information to better understand how our DNA functions in the body, and how it relates to diseases such as genetic disease and cancer. Understanding is the first step in being able to control disease by therapeutics.