[Music] hi guys so I'm extremely excited to share this new platform with you and see how it works for us as a class what's great about this is that you can pause and you can rewatch this video as many times as you'd like and then if you don't understand anything you can just go back and re-watch it again I will be sharing quite a few resources with you on our group and then we'll also be doing some old exam questions as we've been doing in class just to make sure that you guys understand the topic and that you understand the type of questions that they can ask and in exam paper so the topic that we'll be starting with today is genetics and inheritance now as in your exam guidelines it is in paper too and it's about 45 marks which is quite a lot that's about a third just under a third of paper twos marks so you guys do you need to make sure that you understand this work and it can get a bit complicated as soon as we get to the genetic crosses but if you remain focused and have an open mind you won't struggle with it it's very logical that is why I like genetics it's logic it's it's it's a lot of logic and it's straightforward so if you know the basics of it you'll be fine we're looking at it a very basic level now with the metric syllabus but these basics you will carry on if you go study further in university and you do and you do genetics if you understand this you'll be fine then so what is genetics it is the study of heredity and variation in living organisms so basically what that means it is the inheritance of characteristics that you'll get from your parents because of their genes that they have now who started the study of a rarity and variation so a lot of what we know today can be attributed to this guy over here and his name is Gregor Mendel now he was an Austrian monk and he did a lot of experiments on tea plants now a lot of his work that he did is used today the basis of it but sadly none of his work was was ever used while he was still alive it was only after he died that people made use of his findings so why use pea plants so firstly gregor decided on pea plants because they grow quickly so whatever he was looking for he could see the results very quickly after yeast tasted the plants because they grow quickly obviously then they have easily identifiable features or characteristics okay so that means that when you look at people on their life either so in this case they'll either have smooth round seeds or they'll have wrinkled raisin like seeds the seeds will be yellow or they can be green the flowers can be purple or they white and then you also could look at the the seed pods themselves position of the flowers and then whether it was a tall plant or it was a short line these are all of the features the the easily identifiable characteristics that Mendel looked at then another one is that they could either self pollinate Oh what Mendel used was the fact that they could cross pollinate so this was very helpful to him because he could literally cut off the anther of a purple flower and take the pollen and deposit it on a white flower and then cross pollinate them like that to see what features would come out now with his pea plant experiments Mendel was able to formulate two laws so the law of segregation and the law of independent assortment but will not be looking at those yet I just want to run through these definitions these terms that we'll be using throughout this chapter they are quite important to know and understand the work so the first one we'll look at is Lu so what is an allele it is an alternative form of the same gene they contain different info about the same characteristic or trait so usually you'll get well you will get one from your father and one from your mother so let's look at this diagram and so this is a chromosome in one cell and this is the other you could also just imagine that they are two more because this could be at the end of meiosis two specifically telophase 2 so we just said that an annual is the same gene but a different characteristic or trait of their gene so on this chromosome this light blue area would be the allele so if we use this diagram as an example this area of a year would be the annual the gene would be for eye color and then the trait that this specific chromosome is carrying on that Lu is for brown eyes so this one could be for example for brown eyes and this one for blue eyes because it is the same gene just with a different trait or characteristic I hope you guys understand that now if we go back and a locus so what is the locus it is the area where one gene is located now going back to this diagram again the gene for eye color specifically on this chromosome sits right here there is the location so locus could mean location the location of the gene okay so the location of this gene is on this chromosome right here and it is the gene for eye color the gene for hair color on this chromosome the locus sits over there and no homozygous and heterozygous hand in hand with dominant recessive and all of these traits so if I go through these definitions and you guys do not understand them you do not worry you will by the end of this video hopefully so what does homozygous mean so we know by now that homo means same and then zygous is full zygote so you know a zygote is formed after fertilization has occurred you get a zygote so the same zygote basically so when two alleles are the same for one trait example a red flower the color red from both parents so both parents carry the trait for a red flower that's a horrible flower so they are the same color the same trait then heterozygous hetero means different and then as I go as I guess you know what that means so when two alleles of a pair of genes are different for a trait example one blue flower Prairie parent crosses with the red flower parents so you've got a parent that has the trait for a red flower and then you also got a parent that has a trait for a blue flower so in this case they are heterozygous because they are different then we also look at dominant trait so it is the stronger trait and it will always overshadow the recessive trait so think of something that is dominant this is overpowering it will overshadow it takes over that is what a dominant trait does then the recessive trait is the weaker trait and it will only come through if these two of them I'll explain this to you now and then the recessive trait is always domina by a dominant trait so if we use Mendel's pea plants as an example here so a tall plant versus a short plant so a tall plant is always dominant over the short plant and how we show this in genetic crosses is by using the first letter of the dominant trait to show this symbol so in this case tall is the dominant trait so the first letter is a T so it is shown as a capital letter T the short plant will then be represented by a lowercase letter of the dominant trait so in this case short will be a lowercase T now remember you get traits from both your parents so one from the maternal side and one from the paternal side so your Poppa and your mama your spelling and writing from your Papa your mama so let's say your mum has the trait in this case the pea plant the the one from the mother or the female has the trait for being tall so that is the dominant one and then the father has the trait for being short so it will be written like that so one from your mom and one from the dead now remember I told you the dominant trait over always overshadows the recessive trait so that is why the plant will be tall and not short because it has that dominant trait now in this case because there are two different ones we call this heterozygous okay because they are different if it was for example the mum has the two dominant gene as well as the father they would be the same so we would call that homozygous and then if let's say the mom was short and the father was short then you'd have a homozygous short plant because there is no dominant trait to overshadow that one it's just these two and that is why here in the definition weaker trait and will only come through if there's two of them so only at least two recessive traits will it be homozygous short and will the plant actually be short in this case if it is heterozygous two like this the plant will still be tall because that dominant trait completely overshadows the short one over there and if it's homozygous - obviously there's two dominant traits so it will obviously be tall now just for interest sake you can you can go look at this on the internet yourself there's quite a few characteristics or traits that you can look at to see if it's dominant or recessive but in humans just won't interest like a Clifton so having a button basically is dominant over having no clift so if you've got a Clifton you have a dominant trait if you have a widow's peak so what is that that is basically a v-shape of your hairline on the forehead that is a dominant gene if you have a straight a line that is a recessive gene brown hair or darker has dominant over blonde a brown eyes dominant over blue eyes so just more interesting so for example if you have a recessive gene let's use this as a as an example if you have a recessive gene for that recessive gene to show it has to be homozygous so let's say having a widow's peak is represented a capital W and having no widow's peak is represented by a locate lowercase one so in this case it being recessive it has to have two lower cases whereas if it's dominant it can be a capital W and a lowercase W or it can be homozygous dominant with two w's same with brown eyes or blue eyes so if you've got brown eyes it will be a capital B with a lower case because it can be heterozygous or it can be homozygous dominant like that but if it is recessive it will definitely be homozygous recessive with two lowercase B's because as soon as a capital B comes in it's going to overshadow that completely and you will have brown eyes the next two definitions that we'll be looking at is the genotype and phenotype so this genotype is the genetic makeup of an organism and is the information that is present in the genes so Geno stands for genes okay this is a genetic makeup of an organism and it's the information that is present in the genes this is a trait that cannot be seen when looking at an organism so these traits would be for example a tall plant or a short plant that would be the genotype of a pea plant okay it being tall or short now the phenotype Sophie no means the physical appearance so the features Ino features that as pH if V no sound features okay what you see when you look at an organism this is determined by the genotype obviously if the genotype looks like this you will see a tall plant if you see a genotype like that it will also be tall you see a genotype like that the plant will definitely be short so Mendel's laws the law of segregation and the law of independent assortment now what does that mean now the law of segregation means that during meiosis the chromosomes separate leaving each cell with a single allele for each trait when to al use of a pair are different one is dominant over the other recessive trait so this is what Mendel found basically now if we look at meiosis at the end of meiosis one so this would be meiosis one and this would be meiosis two so at the end of meiosis you would have had at the end of meiosis one you would have had homologous chromosomes separating okay so these guys were Molly B's chromosomes then they separated one went to the one pole and one went to the other pole now on each of these chromosomes would be an ally don't get confused with crossing over and alleles now so I remember an Lu is different characteristics of traits for the same gene so on this side of the chromosome there is a trait for let's use hair color okay and on this side is the same carrier with the same gene also for hair color this side might be for brown hair and this side might be for blonde hair and same here remember these were Molly B's chromosomes so the locus for hair color the Lu would sit on the same spot basically so this could also be for brown or blonde hair depending on what you think okay so that is what the of segregation means that they'll always be an allele for the same gene just that the trait will be different either for brown or blonde day then that brings us to the law of independent assortment so what this means is at the end let's say you've got so once again there's a new for for hair color okay so red represents hair color now you can also have another trait that's also on this chromosome or another gene let's Saturday for the Lu now we can say that this represents eye color now what the law of independent assortment means is that one value so this angle over here will not influence the allele over there so whatever hair color is here will not influence the eye color there is what makes meiosis and genetics so interesting is that they are such a large there's such a large amount of variation that can occur because these I mean brown hair or blonde hair can be combined with brown eyes or blue eyes this combination it can go either way if you understand what I'm saying so the law of independent assortment means that whatever hair color is it won't influence the trait for eye color that is what independent assortment means and this is where we will stop with the first video let me know if you guys have any questions and we look at that [Music] you