What is a sunburn? Featuring Olympic Gold Medalist Misty Hyman


Misty (left) and me getting ready to swim

In this two part series, I partner with my friend, Olympic Gold Medalist Misty Hyman, winner of the women’s 200 meter butterfly in the 2000 Australian games.  Misty currently coaches private lessons, leads swim clinics, and gives motivational speeches around the world.  Misty was also recently named the senior assistant coach for the Arizona State University swim team. In her spare time, Misty extends her passion for swimming into the community as a spokesperson for FitPHX and encouraging everyone to learn how to swim.

Swimmers, as opposed to scientists, spend a lot of time outside.  Whether in the pool, by the pool, or in and around the beach, swimmers have a thing for the outdoors. With the outdoors, comes the sun.  With the sun, comes the possibility of a sunburn. And in Phoenix, where there are nearly 300 days a year with sun, a sunburn is even more likely. We all know that you should wear sunscreen to avoid getting a sunburn, but most people don’t know what a sunburn is or why you want to avoid it.  That’s what I’m going to talk about today.

sunburned_hubbySo what is sunburn? Sunburn is a response to the UV light of the sun.  The UV light is a damaging agent to DNA, the genetic code within each of your cells responsible for making your cell function properly. If there is a lot of DNA damage caused by the UV light – if you are in the sun for too long – this is a trigger for these damaged skin cells to commit suicide in a process called apoptosis. Before your cells die, this damage induces an inflammatory response, which is what causes the redness and the heat that accompany a sunburn. A few days after the sunburn, your skin starts to peel – this is the layer of skin cells that committed suicide peeling away from your body.  To summarize – sunburn is essentially a form of radiation poisoning to the skin that kills an entire layer of skin cells because the DNA was too damaged for the cells to live.


Taken by Nick Sherman and used under the Creative Commons License

Now as you and I both know, you don’t always get a sunburn when you lay in the sun (or a tanning bed, which also using UV light and has the same affect as the sun’s UV rays). Instead you could tan.  Tanning is a defense mechanism of your cells against the DNA damage caused by the sun’s UV rays.  How does it work?  The UV triggers special cells in your skin called melanocytes to redistribute or darken a pigment called melanin.  This pigment absorbs the UV light and protects the DNA from the damaging effect of UV.  If you are naturally darker skinned or already tan, the melanin absorbs the UV light so you are less likely to damage your DNA and less likely to sunburn.  But this doesn’t mean that you should just spend all of your ‘working on your tan.”  The melanin isn’t a fail safe UV protector and DNA damage still occurs.

Now that you know how sunburn and tanning works, maybe you’re thinking about how you’re out in the sun all the time, but you don’t get burned or you burn every once in a while but not all the time, so you must be okay. Maybe not.  When the UV light damages your DNA and you don’t burn, your cells still have to repair this DNA damage.  If the DNA damage isn’t repaired, you could end up with permanent mutations in the DNA of of your skin cells. These mutations may change the function of a protein and affect how your skin cells function.  Let’s say for example that you get a mutation in a gene that prevents your skin cells from dying next time they are hit with too much UV from the sun. The next time you get a sunburn, this cell will get damaged, it won’t die, and it will grow and divide with this mutation. Mutations then have the opportunity to accumulate and at a certain point will have enough mutations that the cells grow out of control and form skin cancer.

This can all be avoided in a number of ways.  You could become a scientist and never have the time to go outside because you’re always in the lab (or in my case, because your office is in the basement).  Since that likely won’t happen, you do have the option to avoid UV exposure by covering your skin with light clothing, a hat, or sunscreen.  You can also avoid spending long periods of time in the sun or limit your exposure to times of day where the UV rays are not as strong (when the UV Index is low).  Either way, the DNA mutations accumulate over a lifetime of exposure, so decreasing exposure or protecting your skin at any age will provide an added benefit and decrease your risk of skin cancer.

Misty’s Message: In the 4th grade, Misty did a science project on sunscreen and won the elementary school science fair.  Clearly, avoiding sunburn has been an interest of hers from early on.  Her advice is still the same as her science fair conclusions in the 4th grade: ” no matter what time of day it is, you should always wear your sunscreen especially when you’re in the pool.” The one exception is swimming at midnight – then you’re okay.

What does DNA look like? Like, really?

Everyone talks about DNA.  And shows those lovely double helix cartoon images of DNA. But when you’re a researcher in a lab, what does DNA actually look like?  How in the world do we see it?


  1. X-Ray crystallography.  To be fair, this is an indirect way to see DNA but it is the way that the structure of DNA was determined (as described in our book club book The Double Helix) so it’s worth mentioning.  Remember when you were a kid and you made rock candy by hanging a string or stick in water that had a ton of sugar dissolved into it?  Well scientists can do the same thing with DNA or proteins – make crystals of them.  These crystals are much smaller than the crystals in rock candy.  Think microscopic.  When molecules are all lined up in the same direction, like they are when they form a crystal, scientists can hit the crystal with X-rays and what bounces around and through the crystal can be detected (this is called a diffraction pattern), measured and transformed to determine the 3D image of the molecule – that double helix structure you see pictures of all the time.  This process is called X-Ray crystallography and for the first images of DNA, the diffraction pattern looked like the picture to the left.
  2. dna_in_cellMost scientists do not look at DNA to the atomic level like in X-Ray crystallography, but rather want to see it inside of a cell. The DNA in a cell is inside the nucleus and certain dyes (such as the Hoechst dye) bind to DNA.  Under UV light, the Hoechst dye glows, showing exactly where the DNA is in the cell.  If you look at the picture to the right, you can see the outline of three cells and the blue DNA inside the nucleus of those three cells. Why would a scientist want to see where the DNA is and what it looks like? You can learn a lot from just looking at the DNA. For example, whether or not a cell is dividing or dying, which can be really important if you want to know whether or not the cancer cells you are studying die when you treat them with a drug.
  3. Scientists don’t always look at the DNA directly inside of a cell either.  For an experiment they may want to isolate the DNA (meaning, take the DNA out of a lot of cells to dna_in_eppendorfstudy it) and then manipulate it in some way (sequence it, amplify it, modify it, etc).  Once my mom asked me how big DNA is when you take it out of cells and work with it in the lab.  Well, the answer is that you need a LOT of it to even see it.  In the lab, we may grow bacteria in 5 ml of growth media, which after growing overnight contains 10,000,000,000 cells.  We then bust these cells open with a detergent (like soap, but not soap), spin out all of the extra bits of cells, and then force the DNA to show itself by adding an alcohol like ethanol in a process called precipitation (if you want to learn more about the details, check out this article).  How much DNA do you get in the end – well it depends, but it’s not a lot, visually at least.  And what does it look like?  See the whitish smear at the bottom of that tiny tube?  That’s the DNA.

Are there other ways to see DNA?  YES!  But many of them are based on dyes like the one described in #2 above.  At some point, we’ll definitely talk about them in the context of analyzing DNA sequence and running gels.  And I’m not talking at all here about “seeing” DNA by determining it’s sequence, even though that’s important too.

strawberry_dnaSo now that you know a few ways that scientists see DNA, it’s your turn.  Grab a lab partner, and isolate DNA on your own!!  Don’t know how?  No problem!  There are a number of different ways to isolate DNA at home, the most common being from the cells of an onion or the cells of strawberries.  The experiments for extracting DNA from ONIONS or STRAWBERRIES are linked. At the end of the experiment, what will you see?  Long strands of isolated DNA from all of the onion or strawberry cells. Enjoy and please share photos and stories of your DNA isolation adventures!