Mutants became objects of fear and hatred.

Kitty Pryde narrating in the story Days of Future Past found in The Uncanny X-Men #141 in January 1980

In her DNA they found the key to her mutant power.

Professor X musing about how Mystique was used to derive special powers for the Sentinel army in the film X-Men: Days of Future Past

* Snikt! X-Men: Days of Future Past spoilers lurk below*

In September 1963 Marvel Comics billed them as The Strangest Super-Heroes of All! Issuing from the minds of Stan Lee and Jack Kirby, the X-Men team of superhuman mutants had as its fictional founder and leader the science prodigy Professor Charles Francis Xavier. Across his iterations in the Marvel Universe Professor X is variously ascribed medical and scientific training but could probably best be described as an expert in medical genetics.

Professor X established a training academy for young mutants as a way to help them in using the powers afforded by their mutations as well as to help organize them to defend ordinary humans from attacks by groups such as the Brotherhood of Evil Mutants. The theme of mutants and mutations permeates all the X-Men comics, graphic novels and movies, which are heavy on societal commentary about what it means to be different.

Molecular biology, DNA, genes and the genome are terms that permeate our own modern culture. The physical bits that we think of as our genes are formed from tiny nucleotide bases that are put together to form chromosomes. In your body you have around 3 billion pairs of these nucleotides, with around 25,000 to 50,000 genes all arranged on 23 pairs of chromosomes.

It is the collections of those genes in your chromosomes that allow you to be the person you are right now with all the physical attributes you possess. Genes can be slightly altered to take on different forms called alleles and the sets of alleles you have in your genes are what give you your specific genotype.

But the real functional role of DNA is to give instructions to the factories in your cells, the ribosomes, for making proteins. Proteins are crucial to life and work in your body to shuttle things within cells, to work as enzymes, to provide structural support and as biological motors. They provide your phenotype, the physical expression of your genotype.

When we think about gene expression for a given trait, it has to do with mutations in the gene pairs. Changes in one allele may lead to expression of a certain phenotype. Humans can adapt to a range of conditions but many factors beyond genetics have important influences. There is variation, then, in the extent of responses and adaptations that a person might have, and genetic influences may not be the dominant factor. That means that the genetic effects will only be revealed, expressed or maximized in certain specific situations.

In addition to the genome (the map of your genes), we have the proteome (the map of all your proteins) and the exome (the part of your genome thats actually expressed). We still have much to learn about what is normal variation within the human gene pool, but this brings us back to genetic mutations in the biological sense.

Mutations can be bad, good, both or neither. It all depends on the broader context. In fact, as journalist Paul Voosen has written, were all mutants. Many estimates suggest humans accumulate 100 to 200 mutations each generation, and advanced analysis of genomic data has been used for over half a century to search for areas in the human genome that have been shaped by natural selection.

Our scientific concept of mutation is not quite the same as the super-powered mutations of comic books, which generally seem worthy not of fear but of envy. In the X-Men comics mutations generate fantastic powers like the healing ability of Wolverine, the chameleon-like shape shifting of Mystique and the control of metals possessed by Magneto.

Yet in the storyline from the 1980 X-Men comic book Days of Future Past penned by Chris Claremont and illustrated by John Byrne and in the movie based on that story, mutants and mutations are presented as things that human society should fear. In the comic book we read that in that bleak dystopian year 2013, There are three classes of people: H for baseline humanclean of mutant genes; A for anomalous humana normal person possessing mutant genetic potential; and M for mutantthe bottom of the heap, made pariahs and outcasts by the Mutant Control Act of 1988.

Of course this fear of mutation in the comics is linked with the fact that real life genetic mutations often are related to disease states like cancer or sickle cell anemia. But genes arent just sitting there waiting to give us diseases. As Matt Ridley wrote so eloquently in the 1999 book Genome, To define genes by the diseases they cause is about as absurd as defining organs of the body by the diseases they get hearts to cause heart attacks and brains to cause strokes.

Evolutionary pressures help propagate and sustain some genetic mutations even when they are linked to disease states. Sickle cell anemia is an inherited genetic mutation of the oxygen-carrying hemoglobin protein found in red blood cells. The mutation essentially reduces the elasticity of red blood cells, affecting the oxygen binding function and producing the cells characteristic curved, sickle shape. These cells have a much shorter life cycle than normal red blood cells, can lead to blockages in small vessels, and generally result in a shortened life span for people with the disorder.

So if its an inherited disorder coming from a mutated allele, why has it persisted in the population? A major suggestion is due to the protective effects of sickle cell anemia in regions where the malaria parasite is present. An important part of the life cycle of the malaria plasmodium is spent in red blood cells and the shortened life cycle of red blood cells in sickle cell anemia interrupts development of the parasite. The condition is therefore protective against malaria and defies simple a simple good-bad dichotomy.

If comics adhered more closely to real life, when evil scientist Dr. Bolivar Trask fired up his electronic mutant detector during the Paris Summit in X-Men: Days of Future Past, it wouldnt have just identified Mystique as the camouflaged mutant; it would registered all of the humans in the room as well. But it wouldnt have been able to tell him with certainty whether the mutations they carry are bad or good. As with the superheroes and supervillains themselves, the answer to that question is more complicated.

All images are courtesy of Kristy Inouye.