hi everybody and welcome back to miss angler's biology class i am miss angler and in today's video we are going to be covering genetics and how it affects your blood groups now if you like this video don't forget to give it a thumbs up and subscribe and turn your notifications on because i'll be posting new content every tuesday and thursday for grade 8 to 12 learners also if you're interested in improving your marks getting an a in the finals and you want a little extra attention and help from me don't forget to join my membership which you can find on my home youtube page so let's begin by looking at the physical characteristics of blood groups first before we get into the types of genetics that control it now in front of you here we have four red blood cells or erythrocytes and you will notice that they are slightly different on their outside appearance and this is because each of them has a different kind of antigen on the outside now an antigen is a protein that we find on the outside of our cells and essentially it allows your body to determine whether or not a cell belongs there or if it's a foreign invader now when we talk about blood groups we talk about the antigens that you have on the outside of your red blood cells and that will tell you the blood group that you are so if you have antigens a on the outside of your blood cells you're going to have type a if you have antigens for b you'll be type b if you are a type blood a b it means you have both of those antigens and we can see both of them on the outside however if you have no antigens for a or b then you are actually o blood type now knowing the type of antigen you have on the outside of your blood group is important for donating blood and making sure that you are a blood match because essentially antigens allow you to give blood to people who fall into the same category as you and then there is also something called a universal donor which essentially means that someone like blood group o can give to all of these blood groups because they don't have any antigens whereas someone like blood group a b they can only give to a b because of their antigen composition now let's get into the genetics that governs your complete and co-dominance that we see in blood groups now the first thing i want to point out before we even begin on the content is what are the allele letters that you need to use i want to stress to you very very importantly here that the letter i's that they use here for the alleles are universal and they are the only letters you are allowed to use in an exam please do not use any other letters other than the capital letter i and the lowercase i with the superscript a b on it that is the only thing you're allowed to use in an exam and your examiner will expect you to use the correct one and not to make up your own so let's break the blood groups into the complete and the co-dominant groups that we find them in now if we start off with the codominant versions if you remember in my previous video types of dominance and i've just linked it above now for you to go and have a look co-dominance means that two characteristics or two traits share equal space in the phenotypic expression in other words it means that your two traits will be equally visible in the blood group or equally visible in the let's say the fur color of a cow and so we see that as an example when we look at blood group a b if you have a look over at the genotype we use two capital letter i's with the superscript a b and they are equally expressed so therefore we write both a b in the phenotype but then we need to move into the complete dominance one and so what's interesting here when we look at the complete dominance is that a and b are co-dominant they can exist with each other but a and b are dominant over the letter o and so what we need to see here is a different kind of dominance happening something that we've learned before and if you look at the genotypic examples if we look at the first one for a blood group you will see here the one i've underlined now that there is a capital i with an a and then a lowercase i the lowercase i represents blood group o and so for example that means this person over here has inherited one allele with an a on it and then one allele that is representing an o and so what that means is this particular person is going to express physically blood group a even though they carry a allele for the letter o and the reason for that is how complete dominance works again it's a law and the law states that when a two contrasting traits appear as a heterozygous mix which is what we see here this is a heterozygous mix the dominant allele will mask the recessive allele and so that means this person will have a blood group likewise with the one below same situation if there is just one capital i with a b it automatically means that that person will be blood group b and we can ignore essentially this case i because it's a recessive allele it's masked that then means that the only way you can be blood group o if you are following this law of dominance is you need to have two lower case eyes you need to have two recessive alleles in order to have this characteristic so there are very many ways they're going to ask this in the exam and generally the questions sort of go along the lines of well if the father is this blood group and the mother is this blood group what are the chances of them having a child with blood group a or blood group b and that's where you would use those genetic crosses that we've worked out before and i've linked my monohybrid cross above to help you explain how you would do a simple monohybrid cross to work that out but another way that they can ask this question is through paternity testing now we've actually learned a little bit about paternity testing because paternity testing refers to testing for someone's father using his genetics and his dna and we've done this in the dna videos where we spoke about how you use a dna profile to determine paternity but you can technically also use blood groups however there is a limitation to this and so i want to really stress this because this can be an exam question and then it can come up they might ask you can you use blood groups to determine someone's father and the answer is simply that blood groups can only eliminate a potential father they cannot confirm a father and the reason for that is everybody else in the world also has similar blood groups just because the father or the potential father is a blood group a and the child is blood group a doesn't automatically mean that that is their child it just so happens that they have the same blood group but that doesn't mean that that's necessarily their child you've got to take into consideration what the mother's blood group was and also maybe there's potentially a different father with the same blood group and so i'm going to give you a couple of questions and we're going to use this table alongside just to see how this would work and so what we see alongside here is a table with the father's blood type at the top here the mothers on the side and then it gives you all the possible combinations like for example if a mother is blood group a and the father is blood group a the only two possible combinations that could be produced are a or o now if you're wondering how did we get just those two values well we need to look at the alleles of the two parents so that means that mom is either going to be a capital i uh with an a on both of her alleles like this um or she can be capital i with an a and then a lowercase i and the same thing before for this dad over here the the the dad that is an a and so those are the only cop combinations that they can be those two parents and so if they are both this option over here their baby will be 100 a blood group no other possibilities but if they are heterozygous like this one if two of their smaller lower case eyes go together then you would end up with an o blood group so this blood group is pretty nifty this table to help you figure this out and so i'm going to give you some examples of things that you might see okay so here's an example a male with blood type a b cannot have a child with blood group o and we can prove that by even just simply looking at the table but i'll also prove it a different way here is the father's blood group a b and if you look through the list going down you will notice that there is no o's present regardless of what the mother is even if the mother down here is an o blood group it's impossible and the reason for that is that means that our father is blood group a b okay so we write it like this that means that when he has children the only possible children that he could produce must have either an a or a b in their phenotype and this is because in order for you to have blood group o you would need two lowercase eyes or two small eyes and so even if the mother was something like this a capital i with an a and then a lowercase i she only has one letter i to produce yes she only has one small lowercase i to offer and so even if she tried to form this child it wouldn't be possible because she only has one the father on the other hand he doesn't have a lower case eye to offer and so this couldn't possibly be his child now as always i'd like to finish off my lessons with a quick terminology recap first of all we looked at antigens and those were the proteins on the outside of your cell that determine whether or not that cell belongs to you but it also determines on your red blood cells what blood group you fall into which leads me to the types of blood groups we have which is a b a b and o and those are determined by the presence or absence of those antigens we then looked at complete dominance now this is the dominance where alleles are dominant over recessive ones and in blood groups blood group a and blood group b are dominant over o whereas codominance is seen in blood group a b where they are equally expressed in the phenotype we then looked at the very specific genotype that we see in blood groups which is where we use the letter i we use a capital i attached with a superscript a b and for the a and b blood groups and then a lower case i for o we then also looked at phenotypes of your blood which means the physical expression of these alleles and lastly we looked at paternity testing which is testing for a father remember that paternity testing with blood groups can only eliminate fathers it cannot confirm who the actual father is now if you'd like to use these particular words to create flash cards i suggest you do it's a lovely way to revise and if you've liked this video i hope that you give it a thumbs up you subscribe and you turn your notifications on and i'll see you all again soon bye