hi everybody and welcome back to miss Angler's biology class I am Miss angler and in today's video we are going to do a introduction to genetics now if you are new here don't forget to give this video a thumbs up like And subscribe and turn your notifications on because I post new videos every Tuesday and Thursday for grade 8 to 12 biology also if you are new here don't forget to sign up for my membership on my YouTube page you can find the join button um on my homepage and you can have a look at the different perks um that are offered being a member things like members exclusive videos live lessons with me question and answer sessions so go check that out if you're looking for some extra help as you work your way through your um metric and into your finals now it's important to point out that this video is an introduction to genetics if you're needing a little bit more detail you should go and look at my grade 12 playlist there you'll find many videos covering monohybrid dihybrid crosses Sex Link disorders a little bit more in depth this video here is going to cover genetics and the basics around it so let's just recap a couple of things first things first we know that in every cell there is a chromatin Network and that chroma network is found inside of the nucleus that we see here now when a cell is undergoing any form of myotic or mitotic division so meiosis or mitosis that chromatin network is going to condense into chromosomes now if you're not so sure what a chromosome is or its structure you should go look back at my meiosis videos which I've linked above now so you can refresh your memory on all of those Basics now a chromosome is a collection of your DNA and you'll have 46 chromosomes as a human and chromosomes are condensed pieces of DNA so that means if I zoom in on just this chunk over here we will find this piece of DNA that has been condensed now DNA is the code of life we know that it codes for all the proteins of the body everything from skin to hair and everything in between is made via this DNA now the sections of the DNA are called genes in other words if I were to take all the information from here all the way down to there that would code for a specific characteristic now it's really important to get this terminology locked down a gene is a type of a characteristic for example your height your hair color your eye color your blood group those are the characteristics that we find in genes and those genes Express themselves physically so that we can see them in people now if you can see them that would be something like your hair color right but you can't see someone's blood uh group you'd have to have a blood test for that but we still say that a gene is the way you express a characteristic it's really important now to clarify this confusion between the word Gene and Le because it's going to make it really difficult if we don't know the differences from this point onwards so first things first as we've established already a gene is a characteristic so I want you to think of things like your height your eye color your blood group but those particular genes have variations or types and we call those things alals and an Al is a variation of that Gene for example you have your eye color Gene and the variation of that Gene would be a blue um a blue-eyed Al a brown eyed alil a Greene eyed Al those are all variations of eye color eye color is the characteristic and the actual physical color itself is the AL or the variation now let's see these alals in action as we already know every human has homologous chromosomes or homologous Pairs and you remember that from a previous video you have two chromosomes um that are paired together and they are paired together because they carry um a Leal that are for the same gene in other words they carry a eye color or they carry your skin color or something like that where they must be grouped together because they carry the same gene now um we're going to get into more detail about how you actually inherit those things but let's just see what they look like physically what does it in a actually look like on your chromosomes so first things first on these two chromosomes that you have let's say hypothetically for example example over here is where we find your Gene for your eye color on your one chromosome that you have you have a blue Al in that exact location and it must be on both sides because both sides of the chromosome are like mirror images of each other and then on your other chromosome you have a different Al let's say you had green eyes on this particular uh chromosome so that's your Al now you will notice that the gene is in exactly the same place on both of the chromosomes which means that it is the same characteristic it's the same gene but the colors are different and because the colors are different we say that those are alals they are different kinds or different types and so what we have here is one gene but we have two two different alals is what we are seeing here two different alals now that we've clarified what an alal and a gene is we now need to look at how do you actually pass those characteristics on and so in every human being you have 46 chromosomes and they come in pairs or homologous pairs the pairs are made up of a maternal chromosome which you got from your mother and a paternal chromosome which you got from your father and what that basically means is for every single Gene in your body you have two alals for that Gene so as an example on here this particular person is going to have a eye color gene on the one chromosome from Mom and then on the other we are going to have maybe a different alal variation maybe a blue variation for eye color on the other so what that means is for every single one of your genes you will have two leals or two versions of that Gene and you are going to pass those onto your children but separately and that comes down to having knowledge in meiosis and so these two chromosomes are not going to stay together based off of how meiosis works the maternal chromosome is going to go off into its own cell over here and the paternal uh chromosome is going to go off on to another different cell that will then continue on in the process of U meiosis this separation you may be familiar with when you think about anaphase 1 where we separate the homologous Partners from each other so now I've gone and I have placed those chromosomes into separate cells and they've taken their alals with them and so that is why when you have children you can only pass one uh of your alals on at a time for example let say that you were male um and it doesn't matter if you're male and your maternal or your paternal is passed on it it's not linked to your sex in other words if you're male you don't just pass on paternal tra you can also pass on maternal ones um essentially if you were making sperm cells maybe the sperm cells that were resultant of this particular cell are all going to have brown eyed alals on them and then maybe all the sperm cells that come from this chromosome are going to have all the blue alals on them and so essentially what I'm getting at here is when you pass on your characteristics you can only pass on one of the two alals that you have at a time you can never pass on more than that because if you do you have created a chromosomal mutation now to take this even further we need to describe these alals in a way with letters and what we do is we use upper and lower case letters to describe the characteristic and in this instance because we are using eye color brown and blue I'm going to use the letter B for now and I'm going to elaborate very soon as to why I'm using Capital B's for the one and lowercase B's for the other that has to do with whether or not the AL is what we call dominant or is it a recessive Al and I'm going to explain that next now that we understand how we inherit our alals from our parents and that we always have two alal for every characteristic we need to now see if these alals come in pairs who gets expressed which one do we actually use because we don't use both of them all the time in actual fact depending on the combination you receive it will determine what you physically look like or what characteristic you have and so that's where we play into a dominant and a recessive Al now when we speak about these alals we often use letters and for now we're just going to use the letter B because it's convenient but you could use any letter when we talk about dominant alals dominant alals are ones that we use with a capital letter when we speak about recessive alals we use a lowercase letter and that's how we tell the difference now how do you know what you are going to physically look like that depends on the combination of your alals now as an example below we have three possible combinations and they come in twos remember because you have to have two alals of every possible uh Gene one maternal one paternal you will see that um out of our first those two individuals you could either have two Capital B's or you could have a capital b and a lower B and then the third individual is two lowercase bees and you can see that their combination actually influences the way they look and we call this influence on the way they look their phenotype which is their physical appearance it is how they look and that physical appearance parents so their color whether they're purple or white is influenced by something called their genotype or their alal and so their alal pairs are important so let's have a look at the first alal pair in this first picture there are two Capital B's which means that this particular plant has two dominant in this case purple alal as the key describes below so that means 100% this uh plant is going to make make purple only flowers no other options the second version is where you have a capital b and a lowercase b now according to the laws that govern how genetics Works which I Do cover in a different video in the monoh hybrid as well as in my types of dominance video which I've linked above now you will see that when you have this mixture you are going to only see the dominant Al or the capital letter Al because the minates it masks the recessive it's going to come out purple the third and final option is two lowercase letters and it's two recessive alals that means that those two alals are going to make a white individual and the only time you can ever have a recessive uh physical characteristic like in this instance being white you need to have two in order to have it now to summarize that when you are are writing out these characteristics and specifically you are writing out the genotype you would say for example that this organism the first one would be homozygous dominant homo means the same dominant means that it has two of the expressed physical characteristics if you have a mixture like a big letter and a small letter we call this heterozygous hetero meaning two different now if you have two smaller case letters you still use the word homozygous to describe the genotype however we say homozygous recessive so that we can tell that oh this is referring to two small letters that are the same as opposed to two big letters for homozygous dominant now as always at the end of every video I like to do a quick terminology recap you can use all of these terms in your flash cards while you study it's the best way to study terminology first things first we looked at the chromatin Network which was a recap of a previous lesson where we looked at that long twisty noodle like structure that has all your DNA it's only visible during interphase and it condenses into chromosomes chromosomes uh you have 46 of them they carry that particular DNA we spoke of earlier in the chromatin Network and they are the ones that uh we will be dealing with mostly when we talk about alals and being able to see them and pass them on and cross in over and stuff like that in meiosis and then we looked at genes which were sections of the chromosome that coded for a specific trait uh that one might be your height your eye color your hair texture and we looked at variations of those genes which we call alals remember that's a variation like you have the gene for your eye color that's the gene but then the variation would be green eyes or blue eyes and so that is the AL then we looked at at paternal and maternal chromosomes which remember you inherit one chromosome from your dad one from your mom and likewise when you reproduce your paternal and maternal chromosomes they must separate from each other so that only one goes into each of your gamuts we then spoke about dominant um characteristics or alals which are the physically expressed alals when there is just one present but if you want a recessive uh Gene to be bre you're going to need at least two um and an example of this maybe in nature would be if you have brown eyes you only need one brown Al to have brown eyes but if you have blue eyes you need at least two small bees in order or or two recessive alil should I say for you to have um blue eyes and lastly we looked at homozygous and heterozygous which refers to um the combination of letters that you have you are either homozygous dominant which means you've got two capital letters let's just remind ourselves two capital letter B's or you are going to have two lowercase that's what homozygous means dominant or recessive heterozygous means you have one capital letter and one lowercase letter now that's all for today's video I hope you enjoyed it um if you like this video don't forget to give it a thumbs up and subscribe I post new content every Tuesday and Thursday and please turn your notifications on so you get the freshest content as soon as I post it and I will see you all again soon bye