Monday, July 16, 2012

Star Trek: Radiation Damage and Infertility

Star Trek the Next Generation (1987-1994) (Picture)
Season 1, Episode 15
When the Bough Breaks

The Aldeans have incredible technology, which has managed to cloak their entire planet for thousands of years. Having advanced technology has come at a price, however. The cloaking device has depleted the planet's ozone layer and its people have become infertile due to DNA damage caused by ultraviolet radiation. The Enterprise reseeds the planet's ozone layer and Dr. Crusher offers them an antidote to reverse the damage done by the radiation. How closely does this match the actual effects of exposure to radiation?

Radiation Poisoning

The only radiation poisoning that people currently have reliable data on is the effect of acute doses of radiation. We are beginning to understand the long term effects of large acute doses of radiation by following the survivors of the WWII bombings in Hiroshima and Nagasaki.

The effects of long term exposure to radiation is not well understood, so it is unclear what would happen to the Aldeans if their ozone layer was depleted by their invisibility device. Let's start at the beginning and see what we can figure out.

What is Radiation? 

In order to generalize a bit, let me explain what radiation is. It can be one of several things:
  1. Electromagnetic radiation (everything on the electromagnetic spectrum, including visible light, microwaves, ultraviolet radiation, x-rays, gamma rays, etc.)
  2. Charged particles, like a helium atom that has been stripped of its electrons and only contains the protons and neutrons in its nucleus. This is known as alpha radiation.
  3.  Energetic lone electrons whizzing through space are what is known as beta radiation.
  4. On occasion neutrons can also fly through space alone. They do not last long though, because neutrons decay with a half life of about 11.7 seconds. I wouldn't worry about neutron radiation unless my room was right next to a nuclear reactor.  
A visual of how penetrating different forms of radiation are. (Source)

These types of radiation can be further divided into ionizing and non-ionizing radiation. Ionizing radiation has enough energy to ionize an atom, meaning it can pull one or more electron away from its nucleus. Non-ionizing radiation does not have enough energy to pull an electron away from a nucleus.

Ok, so what about the Aldeans? In this case, ultraviolet radiation does fall into the ionizing radiation category, meaning it can do DNA damage.


It's very likely that the Aldeans would die from cancer before becoming completely infertile. Ionizing radiation causes DNA damage, which can cause mutations in your DNA. These mutations have the potential to be cancerous.

The same process occurs to make a person incapable of having their own children: mutations to the sperm and egg cells, or to the organs that produce/release the sperm and eggs can cause them to become nonfunctional. Meaning no babies.

 A look at how ionizing radiation damages DNA. (Source)

However, receiving a full body dose of radiation strong enough to eliminate a person's ability to replicate would also do terrible damage to their skin and would almost certainly cause cancer. Of course I'm speculating here because there is no data that I know of that has tracked people who receive reasonably large doses of continuous ultraviolet radiation, so we do not know how it affects their ability to reproduce. There was an allusion during the episode to the Aldeans having a skin condition that they needed medication to alleviate, so perhaps they all have melanoma and are able to cope with it. Maybe that is possible on Aldea.

To keep it simple: it is possible for radiation to prevent a person from being able to reproduce. The question now is whether that symptom would manifest before the Aldeans are on their deathbeds with cancer.

It's a good thing Dr. Crusher had an antidote!

About that antidote... I'm curious to know what it does. It supposedly fixes their damaged DNA so that the Aldeans will be able to reproduce again.

Ultimately, this is a good explanation for how the antidote can make an infertile person fertile again. It is not, however, possible to do anything of the sort today. The challenge is that the damage done to the DNA in each cell is fairly random: you don't know where in a chromosome the damage will be done and you don't know the nature of the damage that will be done.

Without going too in depth with this explanation about DNA damage, I just want to say that the cell has enzymes that are responsible for fixing damage that might be done by DNA. Humans evolved to be able to cope with small amounts of radiation or other factors that cause small mistakes in DNA and there are mechanisms to fix them. These mechanisms are not sufficient, however, to fix large or strange damages, such as those done by a large dose of radiation.

If I were to explain how Dr. Crusher's antidote worked to cure the Aldeans I would say that it contained very advanced enzymes that could pass through the plasma membranes of cells and into the nucleus of cells. These "advanced enzymes" would be able to fix the DNA in every cell, using remaining healthy cells as templates (they will be able to identify healthy cells from damaged cells because they are awesome... or because healthy cells meet a certain criteria. Namely the correct number of chromosomes and chromosome length).

Well... so ends my confused ramble about prolonged exposure to ultraviolet radiation as an explanation for infertility in the Aldeans. I hope some of it made sense.

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