Dystrophin takes 16 hours to transcribe. It is 2.3 million bases of DNA being copied into a 2.3 million RNA base molecule. Not only is that a massive gene (almost 0.08% of your total genomic DNA), it’s also incredible that this gives you a measure for how fast a tiny molecular machine (RNA polymerase) joins even smaller molecules of RNA bases (nucleoside triphosphates) together: 2.4e6 / (16 x 3600) = 42 base pairs per second.
Amazing.
(Here is a nice cartoon simulations of RNA polymerase transcribing a DNA gene into an RNA copy, known as messenger RNA, or mRNA for short: simple version and the more detailed version ).