The biochemical world of our DNA takes up its own 3-D space. As long as it has sugar (food) and oxygen (fuel), it goes merrily about its two tasks of life, making proteins and a copy of itself. Protein synthesis is the day in and day out activity that keeps us going. Duplication is the "as needed" process by which a cell divides under the direction of its own control center. Some cells divide every twenty-four hours or so, and some cells rarely if ever divide. Imagine keeping more than a trillion cells in order! The DNA molecule keeps us going and defines our characteristics. These are our chromosomes, which are the coiled up molecules of DNA. There are also some extra proteins thrown in that help to stabilize the DNA such as the handle that it uses to help it make a copy (called replication or duplication). This "handle" is located at different places along each chromosome giving a distinctive shape to each of the 46 chromosomes. Called a "centromere", its position along the DNA coil helps the folks who know what their doing arrange a picture of the chromosomes. At the ends of each chromosome are special proteins called "telemeres" which break away and release the tips of the DNA molecule. Thankfully this happens and keeps the DNA molecule from becoming too fat and sassy!
A basic premise of life is that all organisms replicate their DNA and pass it on. DNA contains the segments that work (called genes) encoding the information about our heritable traits. Our heritable traits come from mom and dad where our genealogy begins.