What is a mutation? Why do mutations occur?

In earlier lessons, we discovered how DNA sequences form genes that shape our traits. But what happens when these sequences get mixed up during cell division? In this lesson, we'll dive into the world of DNA mutations, how they occur, their impact, and what they mean for life as we know it. What is a mutation? A mutation is an alteration in the gene. Basically what we think of as mutation is you inherit DNA from mom and dad. But remember, you're starting off as a single cellular organism that divides, divides, divides into trillions of cells that make up you. So, we're starting from sperm and egg and getting lots and lots of cells. Every time a cell divides, it has to copy its DNA and pass it on to the next cell. Copy, pass it on, copy, pass it on. And every once in a while, as it's copying all of those bases of DNA, it makes mistakes. Most of those mistakes we never know about. But every once in a while, a mistake occurs in a gene in which one of those bases, one of those coding segments gets altered. And if it gets altered in a gene that causes cells to more rapidly divide, that's a mutation we want to know about. We all carry mutations. There is no such thing as totally normal DNA. Sometimes the DNA can have some little errors or typos, if you want to call it. We're calling this a recipe, a cookbook. And these typos can sometimes be typos that you can still read properly without it affecting what the message is. But sometimes there could be a typo that makes it hard to really know what you're saying. And then you won't be able to read the sentence properly if the typo is significant or if That typo makes a word seem like a different word. And that's when we start running into problems with the DNA and what we call mutations or alterations. Because then when the body is trying to read this DNA, it reads something different and it produces something different than what it's intended to do. In general, mutations are alterations to our genetics in one way or another. So all genes are made of DNA, which has four base pairs. And when we see alterations or interruptions to the normal base pairs that we see in a DNA molecule, that is by definition a mutation. To be clear, not all mutations are bad. If we talk about over the course of evolution, mutations are what allowed us to become who we are. But there are many mutations that are considered nefarious and problematic. And those are the ones that we obviously focus on in the context of oncology. Why do mutations occur? What causes DNA to be altered? In terms of what causes mutations, mutagenesis as the term is overall, there are a number of environmental factors and then there are simply some errors that occur within the cell itself. So things like ionizing radiation, certain chemicals and other exposures increase the risk of mutations overall. And whether or not those last or not within a cell depends upon then the proofreading mechanisms. So whatever the original mutation's cause is, in combination then with the inability of the cell to resolve it, is where a mutation will result. Are all mutations environmental in nature? Cells are dividing all the time, and particularly with some of our faster growing tissues like bone marrow cells, skin, hair, the GI tract lining, those are replicating very fast and very rapidly. And so as those cells are dividing, what is necessary is for them also to replicate their genetic material. That's what then allows one cell to go to two and beyond. And when the replication of the genetic material, the DNA, is occurring, we can have these errors. And that is just simply a fact of life that happens. Now most of these errors are taken care of by the body in and of itself, by the proofreading mechanisms. There are enzymes that will actually monitor a DNA molecule and try to assess for errors. And if they are there, we'll try to correct them and even snip them and recombine them. And all of this is a very complicated biology to ensure that the replication of that material happens well. When that though fails, that is what a mutation is. And then that's what can lead to some of the downstream consequences that we see. I always say that people are the DNA of every individual. And if you want to blame your DNA, who do we blame? Okay, number one, we blame mom and dad, because most of the DNA we got was from mom and dad. But then you have to think about blaming yourself, because mutations can occur in sunlight. Sunlight can actually damage DNA. Now most damage that occurs with sunlight damage to DNA can cause other types of tumors, like melanoma. Cause of that is UV radiation from the sun. So there are examples in your environment of pesticides, of food you eat, of toxic agents. We are all exposed to things that can alter our DNA. And some of us do a better job of repairing. Some of us don't repair nearly as well. So mom and dad are to blame. Things you expose yourself are to blame. And then the third one, which is the hardest one to explain, bad luck. I mean imagine you got a copy of those three billion bases over and over and over and over again. Every once in a while you make a mistake. And it's nobody's fault. It had nothing to do with what you ate. It had nothing to do with mom and dad. It's just that the system put the wrong piece in there. It's a mutation, but it's a random error of copying DNA. And what happens is in myeloma, individual bases become changed and they never get fixed. And if they get changed in a bad gene that causes the cell to proliferate, that's an important mutation that can actually cause a tumor to grow. Dr. Van Ness says mom and dad are to blame. To learn why he blames mom and dad, watch the Health Tree University lesson on somatic and germline mutations found in this course. And to learn more about the DNA repairs mechanisms talked about in this lesson, make sure you watch the Health Tree University lesson on DNA repair genes also located in this course. If you found this Health Tree University lesson helpful, give us a like and subscribe to our channel. You can also watch the other lessons in this course on our YouTube playlist or on the Health Tree University website. To watch it on the website, go to the Health Tree University site, find the Myeloma Genetics, Genomics Module, and then click on the Basics of Genetics and Tumor Biology course.