if our skin cells are constantly dying and being replaced by new ones, how can a bad sunburn turn into cancer YEARS down the line?
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The way cancer works (in ELI5 terms) is that it makes a cell that SHOULD die, NOT die. It instead reproduces and spreads
Cancerous cells are the ones that don’t get replaced actually. Healthy cells die, skin regenerates. If cell has turned cancerous, it will not die.
That’s why a lot of biotechnology experiments are being done on cancerous cells – so they don’t die so often 🙂
(overly) simply put: radiation cause cancer, uv light (some of sunlight) is radiation in very small amounts. Sunlight = radiation, enough radiaton = likely cancer. Ergo, enough sunlight = likely cancer
UV rays cause skin to die because the skin that has damaged DNA will commit suicide. If the DNA is damaged just right it can’t commit suicide and multiplies instead with bad DNA and RNA.
DNA is a blueprint for complex proteins. Imagine a factory sending out bad parts that aren’t well designed. Well you build those parts up for years. It comes to light that it’s been making this thing wrong for years. But its too late, it’s in everything.
You might think that this analogy sucks, but there is a real life equivalent. In the capacitor industry there was a formula that was stolen by corporate espionage. The person who stole it recreated the formula at first at a different country, then later went into business making these capacitors with bad formula. It turns out there is an error (rumor has it is that it was an intentional error in case it was stolen) that makes the formula not a perfect match for the original capacitor. Undercutting the market since no R&D needed to be recouped, this stolen formula cornered a huge chunk of the market spreading all over the world and into different industries. Because patent law is not enforced in China, this formula is likely replicated to multiple companies and we know of only those 2 replications
Anyways this stolen capacitor design was made very very cheap and it made it to most consumer electronics for years. Then we see electronics started failing very very frequently at a certain time after being used. It turns out all the electronics installing this capacitor dies an early death as it isn’t as good as the well designed capacitor that has the correct formula. https://www.theguardian.com/technology/blog/2010/jun/29/dell-problems-capacitors
Your is made up of several layers of cells and at the bottom are cells called basal cells which are the ones responsible for dividing and providing new cells. It’s possible for those cells to be damaged by sun exposure. It’s the daughter cells that transform that are sloughed off.
This is just information I wanted to tag on after reading other comments.
UV radiation destroys DNA that is inside of your cells. Melanin is protective and the more melanin you have, the darker your (e.g.) skin is.
All these other answers are more like ELI22…!
Here’s an ELI5:
Cell have memory.
Some cell bad, forget how to be good.
Bad cell trick other good cell.
After time, too many bad cell.
CANCER
Ya know how the photocopied school handouts get worse every year? Its because every time a copy is made it gets a little messier. Now imagine if teacher spills coffee on the handout and copies that. Now its much worse and every copy down the line will be too.
Cells work the same way. So if the sun spills too much “coffee” on them, the copies become tough to read.
The truly dangerous changes don’t happen at the epidermis level. The concerning damage occurs in the dermis to melanocytes. A group or cluster of melanocytes is called a mole (or a nevus) and a mole is evidence something has happened. That something is when melanocytes are “zapped” by UV *radiation*, this activates them by way of tyrosinase enzyme. Activated melanocytes create melanin, which darkens your skin aka a tan. A tan is itself evidence that your dermis has been exposed to UV. Not surprising, right? Sit in the sun, get a tan. But the mechanism is this enzyme causing melanocytes to create melanin.
The exposure to UV *radiation* causes alterations in the DNA of the melanocytes, which is why repeated exposures and/or too intense of exposure can cause this DNA damage to become carcinogenic.
I’m italicizing radiation because many people don’t seem to understand that UV is high energy wavelengths being emitted from our star, just like gamma and x-ray, and just like those wavelengths of radiation UV will alter your DNA (why you wear a protective lead shield when getting x-rays performed). This is why the recommended amount of tanning bed use is exactly 0.
Also, UV-A and UV-B pass through the ozone layer. This is why you should only buy broad spectrum sunblock, which I think is standard now.
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