An Introduction to genetic mutations in plain english

Thanks in large part to Stan Lee and the Marvel comic universe that he created, hearing the word mutant immediately brings heroic fictional characters such as Storm, Jean Grey, or the perpetually angry but loveable Wolverine to many of our minds. While the underlying story of the X-Men in the Marvel universe has a grain of truth to it, it is important to note that the word “mutant” isn’t synonymous with “super power”. In actual fact, when we call a living organism a “mutant”, it means that it has somehow acquired a slight variation in its DNA relative to the norm. At this point, you might want to read this article if you’re new to all this DNA stuff and would like to get a basic understanding of it before you continue.

Each and every single last one of us humans has a genome or complete set of DNA in which all the information that our amazing bodies need to continually sustain us is encoded. Everything from the instructions required to replenish your immune system cells when they die, down to the instructions that are required to keep your eye color brown (or whatever color yours happens to be) is embedded in your genome. Although each of us have a unique genome, the differences from person to person are relatively tiny. Consider the following numbers to furnish you with a sense of scale as far as the topic of genetic variation from individual to individual is concerned.

  • The human genome is 3 billion nucleotides long
  • There are four distinct nucleotide bases that make up the human genome (A – Adenine, G – Guanine, C – Cytosine, and T – Thymine)
  • Our scientific brethren have estimated that the genome of any two people selected at random from the pool of all of us human beings will differ at about one in every 1200 to 1500 bases or nucleotides
  • In plain english, this means that if you went to London’s Piccadilly Circus and randomly grabbed a white person from Waterloo and a black tourist from Nigeria, their genomes would be 99.917% similar! Crazy, I know.
  • And lastly, it should be noted that understanding this kind of science really highlights the silliness of racism. Think about it for a second. Does it make any sense to spend energy hating another member of the same species with whom you share 99.917% genetic similarity for no legitimate reason? I’ve got 5 bucks that says that has to be the definition of “not intelligent”… LOL

After reading those last few bullet points, the following question might be floating around in your head: “What exactly causes those one in 1200 or one in 1500 differences in the genomes of individuals picked at random?”. It is a good question with a fairly science jargon heavy answer… as usual here on the blog, I’ll attempt to break it down in layman terms for all to better understand.

You see, each cell in your body (besides your sex cells – sperm or eggs depending on your gender) has the complete set of DNA sequences that are required to make you in your entirety. As is true of all things living, bodily cells eventually die and I think you can see that without a mechanism to replace cells as they die, we humans wouldn’t last very long if at all. Nature in her infinite wisdom gave the cells in our bodies the ability to make copies of themselves through a process called Mitosis which is also known as cell division in plain English. During the process of Mitosis, a cell will duplicate the entirety of its genome so that it effectively has two genomes. This cell will then cleave itself in half with each new half taking one genome. As a result, there are now two “identical” cells where there was previously just one. Those of you who have been paying attention might ask the following question: “how does a cell duplicate its genome?”. Good question, and to cut a long story short the answer is that cells contain a protein called DNA polymerase which has the ability to latch onto a strand of DNA and make copies of it. The catch though is that DNA polymerase proteins are somewhat error prone and can incorporate the wrong nucleotide base with a relatively low level of frequency.

Nature in her infinite wisdom also added repair enzymes to cells which fix 99% of these mistakes, decreasing the overall error rate of DNA polymerase to one wrong base in every 10 billion base pairs.


 
These random “mistakes” that are made by DNA polymerases during cell division are a source of the genetic mutations that we’ve all heard about. The weird thing about mutations is that most of them are fairly innocuous/harmless while some of them can be severe enough to cause something as devastating as cystic fibrosis or sickle cell anemia. Anyhow, with a bit of a thought experiment, I think most of us can visualize how minor DNA replication errors that occur in the sex cells, can get passed down from generation to generation eventually resulting in that ratio of one in 1200 base pair differences in the genomes of individuals picked at random.

Well then folks, that’s your introduction to genetic mutations in plain english. From all of us here at chubaoyolu.org, take care of yourselves and each other.
 
 
Without Wax
Oyolu B.C. Ph.D.
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