Tag Archives: DNA

Sunburn – Factoids and Public Service Announcement…

Even when it’s lovely and cool you can still sunburn, so cover up or put on some sunscreen!


I went to a fly-in on Sunday, it was so windy I had to hold my hat most of the day. Other than the flying hat, it was gorgeous weather. Enjoyed watching the planes take off and land. Didn’t get fantastic photos, but I felt like I was on the hunt trying to catch them and get my timing right.

I also learned firsthand just how much debris a helicopter sends flying…


Noticed a few hours after getting home that I was *really* pink. Oops!


After hunting down my aloe and downing a lot of water, I remembered reading something about the specific cause of sunburn.


Sunburn is the body’s reaction to damage to the skin cells caused by UV-B light.


Ultraviolet light damages cells by messing with their DNA.


If there are two thymine (the T of the famous CGAT) bases in a row it can cause them to fuse together. This puts a kink in the DNA strand. That messes with reading and replication and is what either kills or irritates the cells.


(There’s a more complex discussion here if you’re so inclined. I first ran across this factoid in Sam Kean‘s new book, The Violinist’s Thumb. Scientists have found that whether or not damage occurs depends on just where two Ts are stacked together when the ultraviolet light strikes. It takes tiny segments of a second for the damage to occur, which is part of the reason you can sunburn so quickly.)


Almost all animals and plants have enzymes to fix T-T kinks in DNA, but along some evolutionary path mammals lost them. Which is why we all can sunburn. Yay?

There was also a bit of a car show, everything was scrunched together, but I loved the idea of the massively overhauled hot rod reflected in the staid still original paint of a classic car.

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Heroes of Science II

I felt a little silly submitting a second piece to such a slimly attended contest, but I really wanted to do something with Rosalind Franklin’s work. I feel like she still generally gets less than due credit for her contributions to the basis of the study of genetics.

It’s also an eye of the beholder matter regarding the materials I chose.

I’ve seen these stones (if anyone remembers their name please let me know!) sold at many mineral shows, often as little miracles: “look at the naturally formed crosses.” It’s a great example of people seeing what they want to see. While the shape isn’t exact, to me it looks a lot more like that little round view with an “X” from Rosalind’s X-ray crystallography than it does a Christian cross.

(Of course, it could also be an X marks the spot, treasure here! Yar pirates!)

Rosalind Franklinwas a British scientist whose work on X-ray diffraction helped uncover the molecular structures of DNA, RNA, and assorted viruses amongst other substances. Her most famous ‘piece’ as it were, was the famous photo 51.

Photograph 51

This particularly clear X-ray crystallography image of DNA gave Watson and Crick the last piece of information to realize the true form of DNA. She was able to show that DNA had a corkscrew pattern in the shape of a helix- the question at the time was whether it has two or three chains.

Watson and Crick used her photo (the jury is still out on whether or not they got their hands on her work legitimately or not-Watson at least has become well known for his patronizing dismissal of her as a proper scientist) to determine the overall shape and played with the shapes of the molecular bases, realizing that sets of two would fit together with hydrogen bonding while others would repel each other on the same principle.

The double helix model with attracting/repelling bases also illustrated how simple (in theory!) replication is: essentially the strands split apart and naturally attract the right bases, so you end up with two copies of the original.

So a Mendel tribute for contributions to the models of inheritance and Franklin tribute for contributions to the material of inheritance.

I’ve mentioned the series before, but for a quick and dirty introduction to genetics, take a look at Larry Gonick and Mark Wheelis’s Cartoon Guide to Genetics. It’s a fast and fantastic introduction to the subject that gives a nice overview of the subject and it’s historical basis.

The classic text is going to be John Watson’s The Double Helix, which is brilliant of course, though I do find him teeth gratingly egotistical and sexist at times. Take a look at Brenda Maddox’s Rosalind Franklin: Dark Lady of DNA for a good, seemingly pretty balanced view of Franklin’s contrubutions.

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