Mutations | Inheritance and variation | Middle school biology | Khan Academy

• [Instructor] In this video, we're gonna talk a little bit about mutations, and I wanna apologize ahead of time. My voice is a little strange today. I rode more roller coasters than I thought I would yesterday, and I screamed a little bit.

But anyway, (chuckles) what we see right over here is what's often known as the central dogma of biology. It explains how we go from information in our DNA, which is really sequences of nucleotides. Genes are segments of our DNA that code for specific things.

So we see these nucleotides, which we denote with A, C, Gs, and Ts. And every three of them, that's known as a codon, and for every three of them, it's associated with an amino acid. In other future parts of your biology education, you'll go into more depth on the molecular structures of amino acids.

But what you need to know now is the amino acids are essentially strung together. And then they create proteins. And proteins have all sorts of functions in your body. To a large degree, they make you, you. They construct what you are.

So this is a simplified version of how we go from DNA to you, to some degree. Now, mutations, as you might know, even when you watch some movies, these are changes in DNA. You might have seen superheroes be exposed to radiation or some type of chemical, and then they get mutations, and then all of a sudden they have powers.

Well, we don't know about too many mutations that create the ability to fly or to stick to walls. But mutations are a way that we get new genetic information in the gene pool. Now you might be saying, wait, I already know about sexual reproduction. Sexual reproduction creates variation. And that's true.

Sexual reproduction creates variation, but it really just shuffles around the genes and the chromosomes they're on that exist already inside of a gene pool. Mutations are actually changes in the genes. Now, where do these mutations come from?

Well, there are sometimes errors when DNA is copied, but it can also happen from environmental influences, like radiation or other things. Now, as you can imagine, many times, if you were to just all of a sudden eliminate some nucleotides, or if you were to change them into something else, that might be harmful.

All of a sudden it might code for an amino acid here that does not allow this protein to function properly. Sometimes, it can be beneficial. And that's how we can get new versions of genes, alleles, or new genes altogether.

All of a sudden this became that, this becomes a different amino acid, maybe this protein functions better. And then as you can imagine, sometimes, it doesn't matter at all. Maybe the different amino acid here really doesn't change the structure of this protein.

And in some cases, you can even change a nucleotide and it still codes for the same amino acid.