Academics Andre's Research Biocuriosities Books Graduate School History of Science Hot off the Press Igor's Research Interdisciplinarity Molecule of the Month Open Access Philip's Research Philosophy of Science Physics Physicsworld.com
Backreaction Ceclia's Blog at PHD Comics Cocktail Party Physics Cosmic Variance The Daily Transcript Easternblot Everyday Scientist The Evilutionary Biologist Freelancing Science The Futile Cycle Good Math, Bad Math iMechanica in singulo Incoherently Scattered Ponderings Juniorprof Klara Stefflova Life of a Lab Rat The Loom Metadatta Mixed States Morning Coffee Physics Not Even Wrong Notes from the biomass Notional Slurry OpenScience Project Pharyngula PLoS Blog Ponderings of a fool Recombinants The Sandwalk SciAm Observations ScienceBlogs Scientific Clearing House Shtetl-Optimized Three-toed Sloth Uncertain Principles What's New by Bob Park
Summer is here, and we’re all heading outdoors to enjoy the sun. But remember to take your sunscreen, since too much sunlight can damage your cells. Small doses of sunlight are needed to create vitamin D, but larger doses attack your DNA. Ultraviolet light is the major culprit. The most energetic and dangerous wavelengths of UV light, termed UVC, are screened out (at least for now) by the ozone in the upper atmosphere. However, the weaker UV light, termed UVA and UVB, passes through the atmosphere and is powerful enough to cause chemical changes in the DNA.
Ultraviolet light is absorbed by a double bond in thymine and cytosine bases in DNA. This added energy opens up the bond and allows it to react with a neighboring base. If the neighbor is another thymine or cytosine base, it can form a covalent bond between the two bases. The most common reaction is shown here: two thymine bases have formed a tight thymine dimer, with two bonds gluing the bases together. This is not a rare event: every second you are in the sun, 50 to 100 of these dimers are formed in each skin cell!
More from David Goodsell on this molecule here.
Ultimate Scientific Distillations: Deep insight, simple representations Life-Science Fiction
Biocurious is written by Andre Brown and Philip Johnson, since 2005. Content of the weblog is licensed under a Creative Commons Attribution-Share Alike 3.0 License.
I like this choice for molecule of the month; not sure why I like it, but I do.
Question: if the double bond involved in the formation of thymine dimers is also present in cytosine, why are thymine dimers so much more common than cytosine dimers?