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Why is the HULK Green? (Because Science w/ Kyle Hill)

What makes the Incredible Hulk so incredible? His size, yes. His strength, of course. But

I think the real clue to his incredible biology comes from his hue.

Let’s start with why we have a Hulk in the first place.

The Incredible Hulk was created when scientist Bruce Banner was caught in a supposedly lethal

blast of gamma radiation. After that fateful exposure, Banner could be goaded into growing

into a green gargantuan.

Gamma radiation is a high-energy form of electromagnetic radiation. For example, if radio waves’

wavelengths looked like this, then gamma ray’s wavelengths would look like that.

This high-energy means that gamma radiation is ionizing radiation.

Ionizing radiation has the energy to rip electrons off of atoms and molecules, turning them into

ions. It sounds harmless, but when this happens inside our own DNA, ionizing radiation can be deadly.

This radiation can touch off cancerous growth in a cell or outright destroy it. But the

Hulk is a different situation. He must have had his entire genome changed and mutated.

Chromothripsis is the term for when a single catastrophic event shatters the DNA in our

chromosomes and those chromosomes try to reassemble themselves.

Typically, chromothripsis leads to cancer and other conditions, because deletions and

mutations occur when the DNA tries to reassemble itself. But in Bruce Banner, his chromosomes

reassembled in such a way as to transform him into a green beast.

But how?

With a new genome reassembled from a gamma-ray shattering, Bruce Banner becomes the Hulk

through an environmental trigger, or anger. This is almost a textbook example of epigenetics

-- the study of how our environment can affect gene expression.

The more we look into our genome, the more it looks like blueprints and light switches.

For example, we’ve learned that for some genes, outside environmental factors can switch

them on and off again.

Banner’s outside factor is anger. When he gets angry, chemicals affect his transformed

genome in such a way that it creates proteins to rapidly boost muscle size, for example.

What does this all have to do with turning green?

Well, it could be that some gene is being expressed to change the color of the pigments

in Bruce Banner’s skin, but my favorite explanation comes from Sebastian Alvarado,

a Stanford biologist who has worked with Marvel before.

Dr. Alvarado thinks that the Hulk goes green because he’s getting what effectively is

a full body bruise.

Now when you get a bruise, blood cells underneath the skin are being destroyed in some way.

Now, when the hemoglobin in that blood is broken down, it produces byproducts that show

up as yellow and black and blue, and one of them, biliverdin, turns up as green.

So whenever Bruce Banner transforms, he is undergoing an epigenetic event from

a shattered genome that rapidly increases his size, which rips apart muscle and bone

which gives him a body-wide bruise that turns him green. Maybe that’s his secret.

Why, because science! Grah!

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