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You were right all along

Do mutant science teachers really exist?

The answer to this question is yes! In fact, everyone is a mutant! New research shows that each of us carries at least 100 new mutations in our DNA.

Mutant science teacher

What is a mutation

A gene mutation is a permanent change in the DNA sequence that makes up a gene. Mutations range in size from a single DNA building block (the bases A, C, G and T) to a large segment of a chromosome.

DNA molecule

How do you get mutations?

You can get them in two ways:

  • From your parents

You can inherit mutations from your parents. These are called hereditary or ‘Germline’ mutations. This type of mutation is present in practically every cell in the body. This is why some diseases can be inherited.

  • Individual mutations

The interesting ones are the ones that are specific to a person. These occur during a person’s life time from the moment their egg is fertilised to the moment of their death. The ones that occur just after fertilisation are called ‘de novo’ (from the beginning) mutations. These explain why some genetic diseases can be present in every cell in a person’s body but they haven't been inherited. Others can occur at random throughout the body. Most are completely harmless, but some can result in serious diseases such as cancer.

How many mutations do we carry?

JBS Haldane

Way back in the 1930s, JBS Haldane, one of the pioneers of mathematical genetics, guessed that we carry about 150 of these mutations. In those days though, there was no way of proving his theory. Today, new gene sequencing technology has allowed us to find out the correct figure. Strangely, it turns out to be between 100 and 200. John Haldane was spot on!

How do mutations happen?

Mutations can be caused in a number of different ways. They can happen spontaneously when genetic information is copied during cell division. Chemical mutagens or viruses can also cause them. One of the most common mechanisms is thought to be exposure to ionising radiation. This is why ionising radiation can cause cancer.

How does radiation cause mutations?

Radiation behaves like tiny machine gun bullets that can penetrate deeply into cells and strike the genetic material in the nucleus. There are three types of bullets:

  • Gamma rays
  • Alpha particles
  • Beta particles
Alpha, beta and gamma particles

Why are the different types of radiation more or less dangerous?

Gamma rays

Alphas, betas and gammas are very different kinds of bullet. Gamma rays are the smallest bullet: they are tiny packets of electromagnetic wave energy. They can pass through things very easily and penetrate deeply into tissue. Because they are so small and uncharged, they will generally pass through a human body without ever striking or ‘interacting’ with anything.

Even if it does manage to make a direct hit on a strand of DNA it will usually only damage one of the strands. The other is left intact and will quite happily repair the damage on the other strand. All very clever stuff! So, gamma rays are the most penetrating, but the least dangerous of the ionising radiations.

Alpha particles

Alpha particles are BIG. They are the nuclei of helium atoms and are highly charged (+2). They move quite slowly so they cannot penetrate very deeply. They cannot even get through the dead layer of cells on the surface of human skin. So, if the source of the alpha particles is outside of the body, they are very safe.

Beta particles

Beta particles cause damage in the same way as alpha particles, but they are much smaller. They are electrons and they carry less charge (+1). They are far more penetrating than alpha particles. When on the outside of the body they can cause damage: a reddening of the skin or in extreme cases a burn. The real danger occurs, again, if the source of the particles is taken into the body in food or is breathed in as a powder or a gas.

All of these radiations, gamma rays, alpha and beta particles, can cause mutations and all of them are found in the natural background radiation all around us.

Can mutations be a good thing?

Yes. Mutations are really important in nature because they are the driving mechanism behind evolution. Without mutations nothing would ever change and no new species would evolve.

In the distant past, there have been bursts of extremely rapid evolution where thousands of new species have suddenly evolved in a very short amount of time.

Is evolution linked to radiation?

Perhaps the Earth has been exposed to greater or lesser amounts of radiation at different times in its past. There seems to be a pattern to periods of rapid evolution: they tend to occur with a period of about 30 million years between them. Coincidence? Maybe, but there may also be a more cosmic explanation!

Earth moves in and out of the galaxy

Most people know that the galaxy is spinning. In fact, the sun rotates around the galactic centre once every 225 million years or so. What most people don’t know is that the sun and the Earth oscillate in and out of the plane of the galaxy about every 30 million years! Perhaps these periods of rapid evolution coincide with when the Earth is surrounded by more stars and is so bathed in more radiation?

Perhaps evolution is, to some extent, driven by our galactic habitat!

The big questions:

What are mutations?

How many mutations do humans carry?

What effect can mutations have?

What are the main causes of mutations?

What role do mutations play in evolution?