Re: How long is a single strand of human DNA when unwound?

Wow! I'm sorry to say that much of your information is correct, but it all refers to different things, as I'll try to explain. First off, the human genome contains 3 billion basepairs divided into 23 chromosomes. A single strand of DNA 3 billion basepairs long would be about 1.02 meters (over three feet) long, which, in humans, is divided into 23 separate pieces (chromosomes) averaging 4.5 cm, each (I guess that's where the 5 cm came from?). The fruit fly ( Drosophila melanogaster) genome is 140 million basepairs long, which would stretch 4.76 cm if it were all on one chromosome; adult fruit flies are about 4 mm long, so the "12 times their length" figure is about right. Note: the size of the genome does not determine the size of the organism, or vice versa, e.g. a lily's genome is over 40 times bigger than that of a whale. Here's an even less useful piece of information: with around 10¹⁴ cells in the human body, all of the DNA in a human, lined up end to end, would stretch to about 1000 times the distance from the Earth to the Sun.