Oh you today's video is all about mutations so we'll cover what causes mutations and what some of their consequences can be now all we mean by mutation is a change in the DNA base sequence so a change in a sequence of letters that make up our DNA code like in this example here where this C has been changed to a G these mutations happen spontaneously in our cells all the time particularly when DNA is being duplicated before cell division like in mitosis two things that increase their risk of mutations though are carcinogens which a group of harmful chemicals like you get in cigarette smoke and certain types of radiation like x-rays or gamma rays it's important to understand though that these things don't always cause mutations they just increase the risk of a mutation occurring to understand how mutations affect our body we need to quickly recap how DNA works if we think of a gene which is just a section of DNA that codes for protein then all it really is is a particular sequence of bases each group of 3 bases is called a triplet or a codon and codes for one of the 20 different amino acids so this codon here ACC might code for amino acid 7 while there's other one CTA could code for amino acid 18 by doing this for all of the triplets and then combining the amino acids together in the correct order we create a long chain of amino acids which can then fold up by itself to form a protein you but if this piece of DNA had a mutation for example this G here changed to a tee then the amino acid that this codon codes for might change as well and this small change can have lots of knock-on effects this is because the overall sequence of amino acids who had now be different and so the protein that it ends up forming would be different as well meaning that it can have a different shape or function for example if this protein was an enzyme then the mutation might change the shape or the enzymes active site so they can't fit the substrate anymore this would mean that it can't form an enzyme substrate complex and so it couldn't catalyze the reaction most of the time though a mutation doesn't have any significant effect this is because they'll often only affect a protein very slightly so it might look a tiny bit different but it still works in basically the same way also most mutations occur in what we call non-coding DNA which isn't part of any gene and so it doesn't code for protein most of this non-coding DNA doesn't seem to do anything at all and we're not really sure why we have so much of it but some of it does play an important role in the expression of genes which is whether those genes are turned on or off for example if we think of a nerve cell there's no need for it to produce hemoglobin because hemoglobins only needed by red blood cells so in the nerve cell the gene for hemoglobin will be switched off which is the same thing as saying that it won't be expressed you the last thing we need to cover are the three specific types of mutations substitutions insertions and deletions if we take this DNA sequence as an example let's start with a substitution mutation which is when one of the basis is changed or substituted for another random base like if there's a change to a T or this G changed to an A as we saw earlier the problem with this is that it changes the code on that basis in and so it could change the amino acid that it codes for now an insertion mutation is a bit different this time an extra base is inserted into the sequence somewhere for example if a c was inserted in here between the T and the a of CTA then this codon would change from CTA to CTC because the a has been pushed along to the next codon this feature means that these mutations are actually a lot worse than substitution mutations are because it means that all the subsequent bases are shifted along by one which alters all of the subsequent columns and so the amino acid chain after that point would be completely different you a similar thing happens with deletion mutations which is where one of the bases is deleted from a sequence for example if this T gets deleted that our DNA will look like this because the T's been removed this a has now shifted one space to the left a hand as a result all of these spaces will also have shifted one space to the left so as well as this codon being different all of these subsequent ones will be as well anyway that's everything for today's video so if you found it useful then please do give us a like and subscribe and we'll see you again soon