CC is on so you will see closed captioning. Click CC button at bottom right to turn OFF. Follow us on Twitter (@amoebasisters) and Facebook! What do you think of when you think of the
word mutation? Do you think about X-men and some really awesome ability? Or…the ninja turtles? We loved the ninja turtles when we were little! We might be showing our age a little bit… But mutations are really not that glamorous. Most people understand that a mutation is a change of genetic material—more specifically a nucleic acid. RNA and DNA are both types of nucleic acids. So how does a change happen? Remember that in DNA, the base adenine (A) goes with thymine (T). And the base Cytosine (C) goes with Guanine (G). And that’s all good, but what happens if the wrong base matches up? Many things can cause
an error like that—-external factors like chemicals and radiation…or internal things
like something goes wrong during DNA replication in interphase, which is a stage that prepares
cells to divide during mitosis. Now while these things can increase the chance that a mutation is going to happen, it is important to understand that mutations are random. If a mutation is going
to be a helpful thing for an organism—which is rare, as very few are helpful—- it can’t
just “will” itself the get that mutation. An organism can’t just “will” itself to get this. It’s definitely not like X-men either. More about that in natural selection. Many mutations are actually neutral in their effect. Meaning they neither help nor harm an organism. And some mutations are harmful. So we’re going to talk about the different kinds of mutations.First we’re going to talk about gene mutations. So DNA makes up genes. And genes code for proteins that influence different traits. So when DNA has changes—-aka a mutation—-then different proteins can be produced and this can affect an organism’s traits. So let’s look at the gene mutations. So first, substitution.That means you have the wrong base matched. So instead of A with T…you can have A with G. Scandalous. You can have an insertion, which means an
extra base (or bases) are added in. You can have a deletion, which means a base is removed. Insertions and deletions have the potential
to be especially dangerous because remember in protein synthesis, we talked about how
bases are read in threes? Well if you add a base or remove a base, suddenly the number of bases total has changed, right? So if you read in threes—depending on where it happened—-
everything that is read afterwards could get really messed up. We call this a frameshift.
Now these were all types of gene mutations, but we also have something called chromosome
mutations. Remember that chromosomes are made up of DNA and protein—-highly organized—and
they have lots of genes on them. All of the body cells in your body each have 46 chromosomes. Human sperm and egg cells have 23 chromosomes. Well changes can occur at that large chromosome scale too. So let’s talk about these chromosome mutations. Just like insertion in a gene mutation—where
bases can get added—–you have something called duplication in chromosomes. These are mutations where extra copies of genes are generated. So extra copies of that chromosome are generated. There is deletion, where some of the genetic material from the chromosome breaks off. Inversion—when a broken chromosome segment gets inversed (which means reversed) and put back on the chromosome. Or translocation (we weren’t
kidding back when we said there are a lot of “trans” words in biology)—that’s
when a fragment from one chromosome breaks off and attaches to another chromosome.
There’s more mutations than what we covered but the idea is that there are
many kinds of different changes that can happen. If a mutation is going to happen, there are
vulnerable times like when DNA replication happens during interphase and also other times too…like meiosis. In humans, meiosis produces sperm and egg cells that have 23 chromosomes. But sometimes those chromosomes, when they’re separating, don’t separate completely. We call this nondisjunction. This results in an egg or sperm that has too many or too few chromosomes…and that can cause a genetic
disorder depending on which chromosome we’re talking about. Different chromosomes contain
different genes so the specific chromosome that is affected does make a difference in
the result. Let’s talk about some real life examples
of mutations. Remember, we said that a lot of times, mutations can have a neutral effect.
Not all of your DNA codes for a direct protein and other genes in your body can influence
whether genes will even be turned on or turned off. Let’s talk about sickle cell anemia. First-
a little background. Hemoglobin is a protein in your red blood cells that helps you carry
oxygen. Well in the disorder sickle cell anemia, the gene that codes for hemoglobin is mutated. If you inherit two copies of this mutated gene (one from each parent), you can have this disorder. This disorder can make it difficult for your red blood cells to carry oxygen because the shape of the red blood cell is affected from this mutated hemoglobin protein. This can
lead to anemia and other problems. But get this—if you inherit one copy of the mutated gene from one parent, you are a carrier but you
don’t officially have the disease. Usually you do not have symptoms. But those that are
carriers appear to have a protective factor against malaria. Malaria is a disease caused by a protist that can be transmitted by mosquitoes. These individuals can still get malaria, but
usually their symptoms are less severe. So, in a way, this one copy of a mutation can be an advantage if you happen to live in an area where malaria is really present. Studying mutations and genetic disorders is a huge field right now. If this kind of thing interests you, there are a lot of careers to look into. In fact, there’s a career known as a genetic counselor. They work to help families that may be at risk or affected by genetic disorders. They do a lot of good in the world. Well that’s it for the amoeba sisters and we remind you to stay curious!