The DNA in a Single Human Cell Would Stretch Six Feet

A human cell is far too small to see, yet it holds a surprising length of DNA. The U.S. National Human Genome Research Institute states that if all of the DNA molecules in a single human cell were unwound and placed end-to-end, they would stretch 6 feet. It fits because of the way it is packed. The DNA is carried in chromosomes, thread-like structures located inside the nucleus of the cell. Each chromosome is made of protein and a single molecule of DNA. According to the institute, the unique structure of chromosomes keeps DNA tightly wrapped around spool-like proteins called histones. The packing matters for more than saving space. Cells must constantly divide to replace old, worn-out cells, and chromosomes are a key part of the process that ensures DNA is accurately copied and distributed when they do.