this video is for the higher level content from d1.3 on mutations and Gene editing with a special focus on Gene editing before we can edit genes we have to know two things we need to know where a gene is located within the genome and we need to know what it does in order to find the location or where the gene is located a process called open reading frame is used so what we're looking for here are characteristic base SE sequences that usually start a gene okay so we can look for patterns here Gene knockout is
the um technique that we'll talk a lot more about that is used to determine the function of the gene because once you know where a gene is located all you have is the base sequences understanding the function of that Gene requires a much different technique the whole thought process of Gene knockout and determining the function is BAS basically to compare organisms with that Gene to organisms that don't have that Gene and see how they are different so we want to take an embryo and it's important that you use an embryo because changes to the embryo
will also be repeated in all the cells made from that embryo right so that's what we want so in that embryo we want to delete one copy of that Target Gene so let's say it's a gene that I'm using with this capital letter B okay um we inherit two alals for each gene so a normal cell would have two copies of that Gene what we're doing in gene knockout is we are eliminating one of those genes from the embryo so the embryo will only have one copy of that Gene not two okay and then we
want to grow it into adults and we want to breed two adults together each that are having a missing Gene so if I put them into a pun Square that's going to look something like this one adult will have B and then nothing where the other cop or the other alil should be and the same with the other individual okay a copy of that Gene and then nothing so you can see that when we complete this punet Square to talk about the genotypes created in The Offspring we're going to find that some of The Offspring
have two copies like they should some of The Offspring only have one copy when they should have two and some of them have no copies so once I have that I can compare those individuals together okay or even this versus this and whatever physiological differences I'm noting I can attribute to that missing Gene and voila I have found the function of that Gene it's called Gene knockout mice make really good um uh experimentation animals for Gene knockout they have a very short generation time time plus they have a lot of the same physical characteristics as
human um so do yeast okay so I know you don't feel like you have a lot in common with yeast but um you do quite a significant portion of your genome and again a very um short generation time so this is Gene knockout now that we know where genes are and what they do we can alter them we can modify those genes using something called crisper and cine so crisper is a segment of DNA it's highly repetitive and very complex and cine is an enzyme um that kind of guides this complex along a strand of
DNA and we'll talk about two applications of the use of crisper one is for finding and altering genes so this is the search and replace method if I have a gene that is faulty or doesn't um or it codes for some polypeptide um that is not the version that is helpful then we might use crisper to find that segment of DNA and replace it so the way that that works is that the target DNA with that faulty Gene is identified right and so we do that with a segment of RNA that's going to be complementary
to that uh to that Gene now once that Target DNA has been identified it is going to be cut okay or cleaved those words mean the same thing and then we need to make some DNA so embedded within this whisper and cine complex it's going to be some RNA that RNA can be transcribed into DNA and then that DNA that desirable version of the gene can be inserted into the DNA and so now that organism has a new or altered section of their DNA and a second application is the elimination of genetic diseases so just
cutting out faulty alals or genes Al together so great examples of that that are CLE cell anemia so going in and cutting out that alil or that Gene um or at least altering it um modifying plants to become more nutritious or tolerant so if I insert a gene that allows a plant to be drought tolerant wow that would be great so that's not really altering a gene that's inserting a a gene that that plant didn't even have to begin with we can also use crisper and casine to create infertile mosquitoes so if you make male
mosquitoes for example infertile by changing the gene necessary for gamet production then you can cut down the mosquito population because you have so many males that are unable to breed it could also happen with the females it's just an example here now Cris bur cast 9 this use of this technology does of course come along with some ethical implications and considerations so I urge you to look into that part a little bit further now theme D is all about continuity and change change obviously mutations and genetic modification is a great example of change but what
about continuity well we have in our DNA some sequences that can be categorized as either conserved or highly conserved conserved sequences are base sequences that are identical across a species or a group of closely related species so if we find that you know a species um all contains the same Gene we would expect that Gene to be identical for all of them if it is a conserved sequence highly conserved sequences are base sequences that are identical over long periods of time and they cross a wider range of species and highly conserved sequences tend to be
things that code for things with unchanging functions so like R RNA or TNA those functions have remained stable over very long periods of time and all organisms need them right so or almost yeah all organisms need them so we would expect um any mutation there to be harmful and not passed along so in this case they would be highly conserved okay now there are some highly conserved non-coding elements but the functions are unclear so it's really a mystery as to why they remain so highly conserved why any changes seem to not be passed along and
they tend to be found in regions of the genome where mutations are rare so there are several hypotheses there are a hypothesis um that links back to the location of those conserved sequences but again I know genetic modification sounds like a lot of change but it's a great idea to balance that with understanding how this um can also result in continuity
