The human genome, the genetic code in each human cell, contains 23 DNA molecules each containing from 500 thousand to 2.5 million nucleotide pairs. DNA molecules of this size are 1.7 to 8.5 cm long when uncoiled, or about 5 cm on average.
You have about 10 trillion cells in your body, so if you stretched the DNA in all the cells out, end to end, they'd stretch over 744 million miles. The moon is only about 250,000 miles away, so all your DNA would stretch to the moon and back almost 1500 times. The sun is 93,000,000 miles away, so your DNA would reach there and back about 4 times!
Interestingly, no more than 1.5 percent of the human genome contains DNA that helps "build" us, that "maps for proteins" as it's called. The other 98.5 percent is junk accumulated through the evolutionary process. For example, 90 percent of yeast genes have counterparts in humans, and there are 223 genes in humans that match those in bacteria but aren't found in intermediate organisms! Apparently, these genes jumped directly from bacteria to humans or vice versa.