hi everyone and welcome back to national higher biology we're continuing with YouTube multicellular organism sleep and we're going on to key area for which is variation and inheritance so this is a key area that often people find quite tricky so I really recommend that you go through these notes still be a lot of new terminology being through about you and try and take some notes highlight the bedside highlights and give a go with the calculations that appear later on so to start off with we were going to talk about the concept of radiation so what variation is is the differences that exist between members of the same species so what physical difference is between your so looking around your fashion for example you should see loads of differences in terms of height hair color eye color that sort of thing between everyone in the room now variation is increased through sexual reproduction because it combines genes from separate parents because you get some genes from your moms some genes to your dad and that's why you'll look like a bit of a mix of them because you're having two different genes or two term assets' of genes being passed into you making your unique individual so before we go on there are two different types of variation that we need to know they are called discrete and continuous variation we look at this first and look at examples of them so first of all the squeak variation those differences in characteristics which is controlled by one single gene so this is called single gene inheritance so different types of discrete variation they fall into distinct groups heeler look like something or you don't or you have something or you don't there's no range between you you'll be able to divide up a room into these distinct grips due to discrete variation so it makes a bit more sense if you look at some examples so for example I color eula have brown eyes blue eyes green eyes that sort of thing it's not a range between them you could divide people up into groups of eye color very easily in that stuff you should maybe do in the classroom it for example another one would be if you look at people's ear lobes you can have attached or unattached ear lobes if your ear lobe goes directly into the side of your face then that is attached if it's not it's unattached so it's not arranged between them you have attached or on attached earlobes that's controlled by a single gene that's why it's single gene inheritance and that is a form of discrete variation I don't want a but more interesting one is earwax so if you were to take a look at your wax you would find you your hat weight your wax or you have dry earwax so again there's not range it's the same grips you have wet or dry and that's controlled by a single gene as a form of discrete baby issue so we've gone to the next type of variation is continuous so continuous is different in two ways first of all continuous variation are still just defin sees physical differences going on but they are controlled by more than one gene so this is known as polygenic inheritance polygenic just meaning many genes these characteristics can't actually just be divided up into groups they can be measured and they have a range of values so first example will show you here is height you're not your one height or an hour type of height there's a range of height between people say in your class or in this petra here you can see this continuous range going from small to tall that's controlled by many sorts of genes so it's polygenic inheritance and you can see the range going on that you can measure as well so Anthony you can measure would be a form of continuous variations for example shoe size or feet plane or something like that those are controlled by more than one gene they can be measured they are not distinct trips and therefore they are continuous variation so first of all the coop for grandfather wouldn't have to look at some more terminology we will be discussing genotypes and phenotypes of different organisms later on and we through what that means so first of all your genotype is essentially the genes that you possess and we will look at genes later on so an individual's alleles for a particular characteristics would be their genotype we're going to look at s alleles next so don't worry about that and come on to that your phenotype is your feed your physical appearance so it's what you look like what those genes have caused you to look like for a particular characteristic so we're trying member this is if you look at the pH or phenotype I'm finger the pH and physical that's a good way to remember it Jesus ain't it's your genes phenotype is your physical appearance so taught fit a Leo woman ago so an allele is a different form of a gene which produces different phenotypes so for example your genetic information we've looked at before is stored in your genes that's where DNA s so you could have an eye color gene but the allele is determine what form of that gene you have so you could having a blue eye color allele and then or blue eye blue eye it and audio coming from your parents which will give you blue eyes that sort of thing now I know it's quite a lot of information gets thrown at you but we're going to look at different forms of alleles and how they actually work in order to produce the phenotype and I'll make a bit more sense to you then so there are two different forms of valios and they're quite easy to see the difference so dominant alleles always produce a certain phenotype think of dominant alleles as a strong form of a Leo they always win over the other types of values and you can tell if it's a dominant allele because they are represented by a capital letter so in this case I've given a but it could be a B could be a T could be anything else it's always a capital letter to show that it's a dominant form of the allele and you'll be told what actually represents as well the other form finale although is called recessive so in comparison to the recessive it's like a weaker form of the audio recessive values will not be shown in the phenotype so it will not be expressed if a dominant allele is present because dominar you'll always wins again you can tell the difference often quite easily because they are represented by a lowercase letter so for example in this one we've been mccally for a dominant allele in this case a lowercase e which was recessive so to compare them again some more terminology for you if you look you get you inherit two different alleles so one for your mom and one for your dad for a certain characteristic if they are both the same form of a Leo so they're both dominant or they are both recessive so in this case they're both capitulated or both little e they recall them homozygous you would have homozygous aliens they're homozygous genotype homework just meaning the same so you can see that it's the same alleles for a gene the difference with all would be if you inherited a dominant allele and the recessive value we call not heterozygous hair true meaning different so straight away you can see a cattle a little E as heterozygous because they are both different one is dominant one is recessive but in terms of what they express the dominant one always wins so even though that recessive allele sort of hiding there it will not actually be expressed but it may come up and then make set of offspring which is what we're going to look at so we would start looking at how these alleles and how these genotypes and have these phenotypes all fit together I have make things hopefully a very easier to understand so we're going to look at the colors of different key plants so this is something that Gregor Mendel studied he first discovered these laws of inheritance and genetics by comparing different colors by comparing phenotypes and seeing what the offspring would be so in this case all you need to remember is we're going to use a again as an allele so capital e of course is Donlin is going to stand for purple winners are recessive little e is going to stand for white we're going to go through one example here and they I suggest you pause the rest of the video and try and do the rest of the calculations yourself just to check how you're doing so in this example here we have a purple pea plant and a white pea plant so your phenotype your physical characteristics hopefully you can tell the phenotype for a purple pea plant would be purple where is the phenotype for the white pea plant would be white so I'm going to give the genotypes of these ones though you don't speak given the genotype you should hopefully know though that in order for it to be purple if capital e stands for purple and Leslie obsessive it stands for wait there are two different combinations a could there be a homozygous dominant capital a capital e or it could be heterozygous where capital e little e because capital e the dominant genotype which stands for purple would always win in this case it's homozygous dominant it's catalytic a flea straight forward for white though there is only one form of genotype you could have to be white you'd have to have both recessive alleles inherited because if you had one done then it would win and you'd be purple so of course in this case is Little Italy which means there's a white P part in terms of gametes in terms of what can actually be passed on to the next generation this one's quite simple the matter which allele is chosen they're both the same so only capital e or Dom Danny or purple could be passed on to the offspring similarly for the white pea plant recessive II is the only option there to be passed on so here we actually have a look at what the potential genotypes and therefore phenotypes for the offspring could be is something called a punnett square so basically we use something called a monohybrid cross where we look at the genotype of the Moller the genotype of the farm is split up into the a Leo's it can pass on and we match them together so if we look at the top left just now if we have a cattle Eve from the Fowler and all Italy from the Muller you get capital e little e if you have capital e from the Fowler and let's leave from a molar then you get Catholic le if you start matching these up you can see in this case Cathleen little e is going to be the genotype that comes up no matter which we even swap or across the gametes from the meal I'm from the female so in this case the offspring or what you can call the f1 genotype is definitely going to be heterozygous is definitely going to be beg a little e because there are no other combinations that the offspring could have regardless of hair the gametes get crossed which means F is a hundred percent likely that Cathleen little E is going to be the genotype of the offspring it means they will all be purple because dominance always wins there's a cattle a in the genotype which means they will be purple so hopefully that's made about sense to you we're going to go on to another example here with different genotypes once I gave the genotypes of a pause the video and try and do the rest on your own so in this example we're looking at purple pea plants again and white pea plants again so we saw hopefully the tape and a wait for the tape but this time would be a little bit different and we will have a heterozygous genotype for the purple pea plant so although it still is portable it still has the capital e it still has the dominant allele there's a little recessive allele has creeped in near as well and the way people obviously cannot change it has to be homozygous recessive so this time the gametes that can be passed on by the purple pea plant are it would be cattle a dominant or Leslie recessive and with whitey wait with wait people and only little e can be passed on so again if we do this punnett square it looks a little bit different this time so start from the top left if you cross Kathleen lightly you have completely kathleen little e and with Lydia as well if we will move on to the recessive allele from the farmer that skills was a deference for a combination wave across a little e in the literally and directly and oddly which means our f1 Gio type is good to be a ratio of two heterozygous and two homozygous recessive which we can break down to one to one so it means in this case there is a 50% chance that the offspring of these two plants is going to have a calf Lea little a heterozygous genotype which should make it purple or a 50% chance that is going to have little a little e or homozygous recessive where Shanina is white so in this case F 2 percent chance of being purple 50% chance of being white and that's what we're looking at look at the likelihoods of what the phenotype is going to be from the offspring so let's look at one more year this one is a little bit different where we have a purple pea plant a purple pea pod so obviously you're a phenotype is going to be portable and patil and your genotype is going to be heterozygous catholic lee and here so just catholic literally as well which means both the dominant and recessive forms of the allele can be passed on to the offspring so have a good opponent square and see what the offspring could potentially have in their genotype and what actually means for their phenotype as well so hopefully if you had to look at this best a bit different because you have two heterozygous parents being crossed together in this case if you cross the dominantly and dominate then you get homozygous dominant you cross the dominant in the recessive ear you get heterozygous dominant if you cross the Kathleen likely catalyst Li and your final combination there is the two recessive alleles which give you homozygous recessive so there's quite a range here of different genotypes that the offspring could have so in this case you could have either there is a 25% chance of them having homozygous dominant genotype there is a 50% chance of them having heterozygous genotype and there is a 25% chance of having a homozygous recessive genotype so quite a mechs go on there however what you should hopefully notice in terms of the phenotype is that you get a bit of a different ratio going off because there'll be a 75% chance of being purple and a 25% chance of being white so a three to one ratio when it comes to phenotype that's because regardless if the offspring inherits the Catholic a filet or the Catholic literally that still going to be portal because remember in the heterozygous dominant always wins and bees like a flea even though there is a recessive value it will still be purple the only chance of that offspring be recessive is the final combination will attack the homozygous recessive what allele Italy so that is the the full form of inheritance if you look at em some Banda hybrid crosses and the last thing we need to know is these ratios that we've just looked at will not always work out perfectly and the question you will often get is why would you know why cannot say that it will definitely have a 25% chance of being white if you have four offspring on your winter perfectly match - because you said the answer is no because offspring will not always follow the expected ratio because fertilization is a random map and boulders really important the reason behind that is that you cannot predict which sperm and egg or pollen and off you are going to fertilize together so all those things will follow that for different types of genotype that is the likelihood of what they will get it could be that although there's a one in four chance of being weight it could be every time they are homozygous recessive just entirely by chance because paralyzation is random so that is variation and inheritance so you need to know your different forms of variation you to know how they are inherited by single gene or polygenic inheritance you need to know all these different terms of your phenotype genotype alleles recessive dominant homozygous heterozygous and work your way through parents and offspring generations and you need to know that Y phenotype ratios among offspring are not always achieved perfectly because fertilization is random so let's play a challenge about the key idea but hopefully you get the hang of it for going through this video I've attached our quizzes of some questions mostly to do with terminology that will hopefully help you out so hopefully you understand this one and you get on well with the unit so far and we will continue on with unit to various it thank you very much for lesson folks