Did you know small fragments of DNA are circulating in your blood stream?
These short pieces of DNA are left behind after cells self-destruct. This self-destruction, or apoptosis, is a normal process. In the case of fetal development, certain cells in our hands die, leaving behind individual fingers. Immune system cells leave traces of DNA behind after they’ve tackled invading microbes. DNA can also appear in the blood when people have cancer.
I had the good fortune, last Monday, to hear Matthew Snyder describe this cell-free DNA in a fascinating talk and learn why DNA in the blood can be a ... Read more
A key concept in science is molecular scale. DNA is a fascinating molecule in this regard.
While we cannot "see" DNA molecules without the aid of advanced technology, a full length DNA molecule can be very long. In human cells, other than sperm and eggs, six billion base pairs of DNA are packaged into 22 pairs of chromosomes, plus two sex chromosomes. Each base pair is 34 angstroms in length (.34 nanometers, or ~0.3 billionths of a meter), so six billion base pairs (all chromosomes laid out head to toe) form a chain that's two-meters long. If we could hang this DNA chain from a hook, it ... Read more