hi everyone this is a recording regarding non-mendelian genetics i hope that it is useful for you while studying about non-mendelian genetics and preparing for your lecture examination that's coming up first of all what i want to clarify with saying non-mendelian genetics is that it's different than what we learned before which was mendelian genetics as you recall mendelian genetics was looking at examples of complete dominance meaning where you had a situation where it would be purple times white and then all the offspring would be either purple or white but you would never get anything like lavender or round and uh wrinkled seeds you would get one or the other but nothing in between so when we're looking at the types of genetics problems this is a very useful list if i were you i would write yourself a list of this um so that you're prepared for your exam maybe give yourself some examples so looking at mendelian genetics complete dominance you look at a monohybrid cross which could be purple times white yields purple for example or a dihybrid cross which would be um purple times white um for color a flower and then um long versus round hollow for example oh sorry i'm a little bit sleepy right now it's been a long day in any case then we can also see that there's non-mendelian genetics and as i'm going along today you're going to be able to see examples of those i would write down examples from here or and or from your examples page from your homework assignment um i think that those will be very valuable those are good examples of them okay so let's get started we've already talked about mendelian genetics we're going to take a look at non-bendalian genetics i'm going to go a little bit of out of order because i find that one of the hardest ones for students to understand is gene linkage and so while we're fresh well i don't know if i'm my brains ready but we can go ahead and start thinking about gene linkage first okay so that being said let's go ahead now gene linkage i want you to think what we learned about last time when we were talking about um we're looking at a dihybrid cross okay so we're looking at two characters and it turns out that gene linkage in some respects because it has two characters reminds you of a diver hybrid cross okay but there's differences in independent assortment um what we're looking at is two genes on two different pairs of homologous chromosomes now if you remember this this is independent assortment and it happens during metaphase so metaphase one so here you can see you've got one pair and then you've got another pair and on this example we have red and red on top but there's no reason why we couldn't have red and then blue because remember the first pair sorts independently of the second pair and the second pair uh assorts independently of the first and that'll go with alleles too it doesn't matter um where the dominant ones are and the recessive ones are that they can independently assort as well okay so again these are two genes that we're looking at on two different pairs of chromosomes for example we're looking at a pair here and a pair here and it looks like the big pair has seed color as its particular gene that you're looking at and the little pear has seed shape and you can see how those are related so they can be independently assorted and what we saw from that is this kind of situation now remember this is talking about a true breeding pair the double heterozygote and then we can see if we have two double heterozygotes meaning a self cross then because they are independently assorted you again end up getting all this variation in the f2 generation and we saw that there was with a particular ratio that was indicative of this scenario do you remember what that ratio was if not look back at your notes try to find that ratio for independent assortment of chromosomes in a dihybrid cross we saw it as an example well if you remember it is a 9 to 3 to 3 to 1 in terms of phenotypic ratio that is one two three four five six seven eight nine of uh round yellow one two three of wrinkled yellow one two three of round green and one of wrinkled green so that's what we saw when we were looking at two genes but remember they were on two different pairs of homologous chromosomes now with so many chromosomes out there if you happen to pick two genes and you were curious about them probably the vast majority of time you could assume that and the other gene would be on a different pair of chromosomes but what if it weren't what if it happened to be on the same parent would you see the same results well actually you wouldn't so this is what we can do looking at this we can see what if by chance we're looking at two genes remember we can't see these physical genes they're not labeled pollen length and flower color they don't say that so we have to look at the numbers to be able to identify what's going on so we call the genes linked if they are two genes that are located closely together on the same chromosome of a homologous pair so looking at this we're looking at length and color it shows here they're very very close comparatively why is that important well if they were still on the same chromosome but they were far apart like this well that gives them all kinds of chance for crossing over to happen and so that would give you the impression that we're looking at the other scenario now if we'd see this in the results we would see this kind of situation going on now if it turns out instead the genes were linked closely to each other like this there's very any room for any kind of crossing over to happen what were the chances that this little red part right here or this little purple heart part is exactly where they're going to do the crossing over instead of here or here or here or here or anywhere else well it's very unlikely that it's going to happen here and so what ends up happening is you don't get this very commonly when the genes are so close to each other there's usually no crossing over and so what does that mean you're usually going to get mostly the ones that were already found on the original chromosome big p and big l and little p and little l with a few times that maybe you ended up having crossing over how would you know this if this happened well again with figuring out these kinds of questions it's all about putting together um your organisms and seeing what you get in the results of their crossings of their of the parental crosses so let's see how this would be seen in the offspring that we would have to test this subject out okay so first of all you can see in this table we have the phenotypes that are possible with these particular genes in the next little column over i'm putting the possible different genotypes that you could have to be able to make these phenotypes and that's what you would see are the phenotypes right that's what you'd end up seeing you can't tell with the genotypes but what does it mean in terms of this okay so if you were looking at a situation where we're independent assortment you would expect this kind of situation this would be your prediction you would expect a nine to three to three to one let's take a look about how this comes up to be nine to three to three to one all you need to do to be able to figure out the ratio here is take your number that you're interested in and divide it by the smallest number in this case we're doing 215 divided by 24. or in the second example we'll take the number that we're interested in 71 and we'll divide it by the smallest number it's the same for the two middle ones of course and at the end here we're looking at the numbers that were interested 24 divided by the smallest number so go ahead and calculate those figure out what they would be if you went for rounding i'll bet you're gonna see that this calculation would be pretty close to nine these two would be pretty close to three and this one of course would be one so this is the ratio that you would end up seeing if you were looking at independent assortment this is what we would expect to see if you had this many offspring however now you do your experiment you take down the data as to what actually ends up happening in terms of your plants and this is what you observe you end up seeing this number this number this number and this number well looking at this one that is way bigger than you see over here and this one is way bigger like compared to what you'd see over here and these two are much smaller so something happened here you'd expect we'd have a closer kind of range or ratio so take a moment and let's figure out what this ratio is to so we're going to take the biggest number here that we're interested in divided by our smaller number and figure out what that is now the next thing we're going to do here is take our number of interest and divide it by the smallest number which of course we know is going to be 1. and then if you take this last number here and you divide it by the smallest number again you're going to see you get a number right is that anywhere close to nine to three to three to one i bet you're gonna find out it really isn't especially you already know these are gonna be one to one if i'm not mistaken it's around i don't know 13 or so to one to one to two point something it just isn't a nine to three to three to one well what can explain these different ratios this one versus whatever you got here well the ones that are higher like these two right here those were found on the original linked chromosomes those are the ones that we first found and these two middle ones are like when you found the crossing over so let me show you the picture on the previous page again oops let's go ahead and clear off this so you can see a little bit better when we get to the previous slide here remember this is what we originally saw these are linked and these are linked so we're going to find mostly these mostly big p and little uh a big p and big l and little p and little l and then a few that might be mixed up so let's take a look and see if that's right remember big p and big l and little p and little l we're gonna find mostly those those are the ones that are linked and then by chance we ended up having some that had some crossing over so the hallmark of gene linkage is when you look at a predictive number and your observed offspring doesn't match that and it's really in this kind of pattern big little little big then you know that you've had gene linkage why is this useful well it turns out that scientists have used this when they're trying to figure out which genes are on which chromosomes so for example if people are interested in which genes are on which chromosomes maybe there's the gene for autism if there is a gene maybe it's on a particular chromosome and then you look at another disorder and you say well do we get the same kind of ratios if we get a ratio that's a predictive number like this then it tells you no they're not on the same chromosome but if you see something like this looks like they're on the same chromosome so it's a very long tedious task but you can get lots of information from it gene linkage helps that way okay so that was gene linkage here is a second kind now imagine that you're looking at this kind of non-mendelian situation you got your flowers nothing looks too unusual you've got a red you've got a white and your expectations would be that okay as a result of this crossing one of these is going to be dominant but you think well maybe it should be red or maybe it should be white who knows and then you watch and you get their offspring and you get this voila not what we were expecting you get something else so this is called incomplete dominance it's where you have pink uh sorry red and white and you get pink we know this as an intermediate and write that down because it's a really important term it's going to come up again later on on my slides so this is an intermediate okay now um one might think um well let's see what should we use for letters and um in the examples that i'm showing here i'm going to scoop back for a moment here in the examples that i have here you have big r big r little r little r and big r little r what we've used in the past kind of would tell us that red was dominant so i don't know if i like this kind of system of using big rs and little rs it makes it sound like the red a red flower is dominant and the white is recessive we know that's not the case because we got something completely different going on here now we look here we see that we've got the red and the white and the pink this is why i use this particular symbolage in this example but i don't really particularly care for it so sometimes what i will describe it as is this maybe what we should do instead of this is start off here and well let's get away from flower or red at all because i've seen this before where you use r one now normally this would be superscript can't write that in here though r1 r1 that would be red and then this one would be r2 r2 and i think they're trying to show that these aren't dominant over each other by using the lower case so that means this one would be r1 r2 honestly i don't particularly care for it either because the r is still there it tells me something about red for some reason one thing i think is good is you can see the combination of letters here that's one and two showing that they are an intermediate of it perhaps a better way of doing this and again this is a little bit challenging maybe it's f1 f 1 meaning flower i don't know it could this could be confusing because of the f1 generation i suppose so and then call this one f2 f2 so based on the logic we had before what would this one be remember it's going to be the intermediate so we would use f 1 f 2. okay so i don't know i mean the fortunate thing about this particular example is this one is the one where you have a little more latitude to use whatever letters you want um because you can see all the reasons to think this is a little bit confusing so again the reason why i chose this at first is simply because that's what was used in your book though i'm not that much of a fan of it now taking a look at it here this right here is called incomplete dominance you can see it's not complete because they always be red or it would be white now one of the things that people get confused about is they think well if this is the case they might think of it as blending but that's a bit of a problem let me see something here right here um it's a bit of a problem and the reason why is because if they were blended if they were paint for example you had red paint and white paint you mixed them together you got pink paint are you ever going to get red and white back well no but in this kind of inheritance you can and so it's not blending let's find a better term for this instead so the heterozygotes again in this case the two different letters it could be f1 f2 right the traits are expressed in a phenotype as an intermediate of the two alleles so some examples like we just talked about are pink carnations or snapdragons notice here excuse me if this is our f1 generation the one that we just finished with and we have them make gametes then you notice if you put the uh a self cross together so a pink times a pink to it with each other you would get your red your pink and your white back that can't happen with blending so we know that these are very separate alleles but that they when together are incompletely dominant and that's why they appear that way now we've seen an example that i think is a pretty good one in terms of hair texture when we look at that you have basically three main types of hair you've got straight you've got wavy and you've got curly so it turns out that they are incompletely dominant as well so what that means is that if you have a straight and a curly haired person have offspring they're going to have the intermediate and so there's really not a particularly good way of describing this without using these kind of letters that's kind of why i like this one there's h and then there's h1 you could have h1 h2 or this could be h1 and this could be h2 okay so honestly it's just to show that they're different but the important part is indicating where that intermediate is okay that's the intermediate and that's the one that should have combinations of two letters making them heterozygotes all right so now taking a look at incomplete dominance we've had some pretty fun examples flowers and hair texture turns out there's some pretty serious medical ones too so this is a disorder called hyper cholesterolemia well you can imagine when we're looking at hyper that means more and then cholesterol cholesterol anemia in the blood so it really literally means dangerous high levels of cholesterol in the blood so if this happens to be a blood cell right here on our um blood cells what we have are proteins for many reasons we've learned about transport proteins so far these are receptors so something can attach to them kind of like a ship docking at a at a port or something like that so here we've got the um ldl which we already know is the low density lipoprotein that's the least healthy kind of cholesterol and what happens is it docks into a receptor and then what ends up happening is this cell is going to break it down so that decreases the amount of cholesterol in our bodies this is what happens to us every day okay and unfortunately there are people who can inherit the other part of it so this one's little h little h but remember these are incomplete dominance okay this unfortunate person does not have any of the receptors and so what that means for this particular individual they can't break down the ldl receptors and they'll die of a heart attack as a baby very tragic now of course you can see why that's severe when we look at the mild disease um you can see that there's about a half of the amount of receptors on this particular cell compared to what's going on in the normal so it's in between right it's an intermediate and so it does have the ability to break down the ldl but this despite diet and lots of other things this person will probably die of a heart attack around 30 years old unfortunately so mild i guess but 30 sounds really young to die so this is an important example of incomplete dominance now there's also multiple alleles and codominance when i say multiple alleles um let's kind of define how many alleles we've had in the past when we looked at flower color we had purple and we had white so we used p and little p when we looked at tall for plants we said tea and little tea when we looked at say for instance the shape of the sea the seeds in peas we learned at r and little r right so there's always been two alleles that we've talked about every time in this case what we mean by multiple alleles is that there's going to be more than two possible alleles existing in a population so a good example of this is going to be our blood typing so what we learned is that there's blood types where the alleles are i a ib and then there is lowercase i well notice here that we have the i and the lowercase i that is going to be complete dominance so we could in addition to writing multiple alleles and codominance we could also say a and there's also complete dominance here too so here's where we're taking a look at the actual blood types which are the phenotypes themselves you know you never walk up and say in somebody and say what is your blood type and you say oh i'm an iaia oh nobody knows that what they know is i am a type blood or i'm b type blood right so that's the phenotype and you could see that when we did our little um slides for blood when you talk about this here a person could be a type blood but have these two genotypes right and here is a good example put a little star here this one and this one these are good examples in addition of being let's see if we can write it down here complete dominance oh i hope i spell it right and i can't see it got it right can't believe it so right here both of these are examples of complete dominance this one and this one because the a is completely dominant over the o allele to make a phenotype and the b is completely dominant over the o allele to make b okay so here we've got again our multiple alleles there's three of them we've got complete dominance now the last question is where's the code dominance well you can see that right here in let's see we'll put us a little check on that one there oh no let's move it can i let's see if we can undo oh thank goodness i missed it this right here is the example of um codominance and you see it right here because in a b both of them are being expressed you're going to have a and b in the heterozygous individuals now for a person to be o they're going to have two lower case eyes if they have something else then they're going to be that blood type all right so my next question for all of you that i'm going to pose is what's the significance of this we learned a little bit about this in lab but let's talk about it a little bit more in terms of blood typing what's happening here is the body's ability to determine what is a cell that belongs to this body versus a cell that is attacking and so this is an immune response and it's kind of a funny one it's not well understood why we have um these kind of responses to other blood types it's not really completely understood however um let's take a look at what's causing the response so if you have an a-type blood remember these are the genotypes here that means that you have proteins on your red blood cells and those proteins have carbohydrates on them so the kind of carbohydrate you'll have is carbohydrate types type a if you're a b type person you have proteins with carbohydrates and yours is a type b carbohydrate if you happen to be an a b person that means you have a type carbohydrates on the proteins as well as b type now if you're an o type person that means you have neither kind of carbohydrates on the proteins there so what does this mean for you well this really becomes important when we're talking about if you need a transfusion so say for instance we will hopefully this never happens but if it were to happen then what would happen is you would get a um if you have a donor then we would want um to have the right kind of donor okay and sometimes it's easiest for me to think about much more simply what would happen if you had a a carbohydrate type a and what's happening with the carbohydrates on the outer surfaces of these what i like to think about is that okay i've got carbohydrate type type a if i have um if i'm given some blood that has the same kind of structures or less then i will be safe okay so let's take a look at this if i'm up a type person that means my structures look like this if i have an o type blood well they have fewer than what i have so i'm safe and you can see that there's no coagulation right here if right here if i have an a type blood right and uh it's given to me that means that it's the same so there's going to be no coagulation if i have on the other hand a b type blood well is that the same no so we're going to have coagulation that's going to happen if we have an a b type blood well does it have the same well yeah it has a but it doesn't have less because it has one more it has b so there's going to be coagulation so where they're all clumping here that's not good if you have a b type blood and you're given an o well a b has these structures but there's less of them on o so we're just fine if you have an a type blood given to a b type person that's not good they're not the same and they're not less if you have a b type blood that's the same so we're okay if you're an a b type lead well you have the same you have b but you also have more you have a so there's going to be clumping there with a b type blood you've got carbohydrates type a and b what that means is that for each of these they're going to have well let's see either the same as in a or as in b or as an a b or they're going to be less for o so all of those are fine when you're an o type person then what that means is that you will um if you take an o type blood you're the same you're going to be fine but the other three all have more structures on their outer surface than you do and so you get agglutination so it turns out that having certain kinds of blood types makes it easier or more difficult um to donate your blood or i should say not necessarily to to donate but to be used okay so if you're a person who has a b type blood you go into the hospital you can take any kind of blood that they give you assuming that we're not talking about our rh factors remember there's rh positive and negative we're not even getting into that right here but you would want to have less so that would be a negative right okay that you could get um so these people can accept any type blood in contrast o type blood is the universal donor and so that's why especially if you're o negative because you have that rh factor situation there are no structures on the outer surface of your red blood cells and therefore they would love to have your blood because your type of blood can be given to anybody and not have a reaction if you're o negative so in terms of just talking about letters o is the universal donor and a b is the universal acceptor okay so um that is an example let me go back to that multiple alleles codominance and of course we just briefly mentioned complete dominance in the case of i a lowercase i and i b lowercase i there's three things going on there okay next one here's another example of codominance so blood typing is not the only one but here's a good one it's about sickle cell anemia sickle cell anemia is a disease and it has two alleles they're named hb a and hbs hb is for hemoglobin okay s is for sickle now for a person who's normal understanding that this is their genotype is very helpful that's why i would include this on your sheet of examples so that way you don't get confused when you're working on your test uh carrier hba hps we call that the heterozygous because they're different and then the person who actually has the disease is sickle cell hbs hbs now what's happening here with sickle cell anemia what is it all about we said it has something to do with hemoglobin molecule well you remember looking at our red blood cells a long time ago that they were kind of a little bit like a donut that had not been completely punched through that's because the nucleus was removed as it matured the reason why that is is it's got lots and lots and lots of these um hemoglobin molecules that it uses to transport oxygen and being really small blood cells helps them get through the blood vessels so here we've got hemoglobin we know it's a protein you can see that it's got four parts to it so and each one of those is called a heme group so that's where it gets the name hemoglobin and then it's globular in shape and then each one of the heme groups is attractive to oxygen so the oxygen binds to that that's right where the iron is so that's why iron is important for people who are anemic now notice here um with a hemoglobin molecule they're nice and unshaped beautifully but if a person has the sickle cell allele that causes the production of abnormally shaped hemoglobin so there's a simple mutation that's happened in the dna at one point in some person's life many centuries ago and what that means is that there's a difference in terms of the overall shape especially under certain circumstances we know that normal red blood cells last about 120 days they're cycling through our bodies and then they're going to be removed by the spleen however when the body recognizes that there's an abnormally shaped cell like this one then the spleen will take up that sickled blood shape um cell um after only 10 or 20 days and because there's so few red blood cells now you might have anemia so anemia has there's different examples of it anemia in general means that you're lacking amount of iron in your body um it can happen to anybody to have anemia women are particularly prone to it because as they have their period they lose a lot of blood which means you lose a lot of the iron associated with it that's why a lot of women get cold hands or have other um kind of aspects about them and so if they take iron that helps them with those little aspects now anemia here in this case um is a little bit different because this is because we're dealing with a genetic issue okay so similar situation but much more extreme well uh also the other thing about anemia is it'll make you feel cold you get forgetful there's certain little qualities about it that uh are very frustrating for people who are who have an anemia now in terms of somebody who has um sickle cell anemia it's a lot more situat different situation it's much more disparaging difficult to deal with so here we have um a normal blood vessel and you have red blood cells that are moving through it and because they're nice little shape they can squeeze through these smallest of vessels known as capillaries okay however when you have abnormal hemoglobin what will happen is the molecules start to link to each other and then they become crystallized and the situations that will produce this are when you have low oxygen um and that might be because of you're at a high altitude or you've over exerted yourself or you might have say some kind of respiratory ailment maybe you have bronchitis or pneumonia at this point when that happens these little red blood cells become sickled in shape and then they can't flow through those smallest of vessels and that causes serious serious problems so it's not just one problem anymore it becomes multiple problems and that's why we call it plyotrophy so codominance is how it is that you inherit this um but plyotropy is the effects that you can have from a single gene so we're talking about one gene having to do with hemoglobin and whether or not it's normal or if it has sickling in this situation what are the possible effects well you can just imagine that if you've got these sickled cells we already said that there would be breakdown um of them and that could lead to physical weakness and anemia even heart failure it could lead to accumulation in the sickle spleen cells in the spleen right which we talked about because they're going to take them out but beyond that it can also cause these clumping of the cells and clogging the small blood vessels like the capillaries which can lead to impaired mental function heart failure pain and fever brain damage pneumonia damage to other organisms rheumatism kidney failure oh you can just imagine it's just it's horrific the things that can happen so a person that goes into crisis you have to be very very careful with them they need to go into the hospital and be monitored very carefully because so many different things can happen there's so much that we're looking at because of plyotropy here um just to kind of give you an idea about this um i was in my light treatment as you can imagine because of my psoriasis and i happened to talk to this woman who had psoriasis that's why we started talking but she started to talk about the fact that she had children and had lost all three of her children to sickle cell anemia it was really sad she said one was 37 when he died the other one was 17 when he died and the last one was a baby when he died and so it was just so sad to think about this woman having to lose her children because of a genetic disorder um and this is one of the reasons that i mentioned to peop g before you know that people might choose to do preconception genetic counseling if they have that available which of course if you know if there's no insurance that's so aggravating to me um we in a very developed country we should have health insurance for everybody i mean that's just a basic basic function of our society right but any case if people don't have it you know they might not have the ability to or feel they have the ability to go get um tested for genetic counseling and so what tragedies that person has to deal with now um you think about it you look at it oops hold on let's go back here you say okay why is sickle cell anemia so prevalent i mean really this disorder it can be fatal and often is right if not just debilitating so people have asked this question like okay this disorder is lethal and this sounds really harsh but why is it then that people who have it don't just die and then it goes away well it's more complicated than that unfortunately it's it's kind of a crazy thing that it doesn't right um so take a look at this this right here is a picture where we're looking at the distribution of malaria and here we have the distribution of sickle cell anemia disease okay so you can see there's a lot of overlap in what's happening here right not exactly but you can see that it has um overlap in it and there's something that's strange that goes along with this for those people who are the heterozygotes hba hbs it turns out that they have higher fitness now fitness we're going to see does not mean i've gone to the gym it does not mean that it means instead i have survived and i've had babies so to be quite frank um i wish we were talking about this in class right now because i'd like to know well how many children do you have i know at least one student who has three um i know of another student who has two i know of another couple of students who have one so that would tell me that the person who has three children has the highest fitness the people that other person and i who have two we have the second highest fitness the people who have one child have the next highest fitness and all the rest of you zero fitness i know that sounds funny but it doesn't really matter but that's the term that's what it means so none of you are fit except the rest of you i'm just kidding of course that doesn't really matter again but that's what we mean when we say biologically by fitness it doesn't mean how many um you know weights or how much weight can you lift or anything like that or how far can you run that's not what it's referring to um okay so it turns out those individuals who are heterozygotes they're able to resist malaria and because they can resist malaria they have more babies right those people who are hba hba well they're considered normal right they don't have that but if you lived in these areas where there's malaria then the likelihood is you could get malaria and potentially die of it if you're a person who has hbs hbs and you get sick well we know even in a country that has medicine like here people can die of sickle cell anemia so we're going to see remember it's always going to be visa around if you could put in your mind on your punnett square hba hbs and then down the side hba hbs and visualize there you're going to get your sickle cell anemia in that bottom right corner always and so it doesn't go away it still is around okay now the next thing we're going to talk about is polygenic inheritance you can already kind of define what's happening in here by understanding poly meaning many and gen meaning gene so this is going to be multiple genes right so it's the additive effect of two or more genes on a single phenotypic characteristic there's not just one gene involved in this it's two or more and the characteristic is going to follow along a continuum remember this is what i was saying early on that made the original kinds of genetics questions so difficult they weren't discreet purple white or round and wrinkled so they were very difficult because they were along a continuum so for example in this picture here you can see that clearly this magazine cover is trying to show that even in a family you can have much variation in terms of the phenotypic characteristic of skin color right you can see people um of varying skin colors who would consider themselves black right in this particular picture what we're looking at is the continuum of heights when we're looking at it from a very short and of course i don't know if i would consider quote-unquote these little people here as part of this group because this is from a different gene but the reality is that people in general have heights that are really really variable in terms of along a continuum so what we consider tall is kind of you know what is that what does tall mean is it five foot six and above is it five foot nine and above is it six foot tall is it that for women or for men or for both so um it's a little bit complicated to figure out what does tall mean right like when i lived in germany for a year um i was not considered tall at five foot eight i was considered kind of on the shorter side actually which was really weird for me because i grew up very tall i grew up to be five foot eight by eleven years old so i was a very tall kid for a long time and then i just stopped growing when we didn't know if it was gonna happen i could have been you know six foot something but it just didn't turn out that way i just stopped growing at that point um now also other aspects like hair color we can see it's all kinds of continuum on there there's other kinds of um of inheritable traits that are also probably along a continuum but remember you can't just say oh it is specifically because of my genes that i'm obese there's the effect of the environment right like for example do people have good quality food around them do they have active places that they can go out and take a walk if you live in a dangerous city you wouldn't want to do that maybe the danger is just from cars driving around or you know maybe it's lifestyle so there's lots of reasons why there can be obesity other than only looking at your genes same thing for diabetes same thing for cancer and autism right so you got to think about this this these are probably all along the continuum and is really completed by more than one gene that we're talking about here okay so let's take a look at skin color because it's a very interesting example here um let me just take off this blue line here okay so what we whoa what we do know is that skin color is polygenic in polygenically inherited we know it's at least at this point we know of three genes and so um imagine that we're looking at two people here and you can see that they're clearly kind of extremes like the very lightest of skin person that you've ever seen without being an albino right and then the very darkest of skin that you've ever seen okay now notice these are two people three genes why do they have six circles of them can you figure it out take a moment and think about it and put it on pause while you think all right so maybe you've thought about it and you've noticed again six circles well and three genes that means we're talking about two alleles for each gene so that person's gonna have inherited one from mom one from dad one from um mom one from dad for each of these genes right okay so if these as the parent generation got together this extremely light um skinned person extremely dark-skinned person that's hard to say all those then what would happen in your f1 generation is you would get this combination of genes and so the the offspring would be medium shaded in terms of their skin color now let's pretend pretend that we're looking here at doing a self cross which we've talked about before that means this person right here has the um the same kind of parent as their significant other okay and so for that reason they end up with a similar shade um in of their skin well if you take this and if you look at it in terms of all of their sperm and egg here we're going to inherit from one individual three genes and from the other one three genes and what you can see is this is the possible outcome for all these different kinds of egg and sperm what you see in this is a frequency table and it's taking this and saying okay well which is you know down here is pretty much the least common and down here is also least common down in this side and then the color that's kind of in the middle is much more frequent right so we're saying you know the very light and the very dark are less frequent on this whereas there's going to be people kind of offspring that are more likely towards the center right and so that's why you'd end up getting likely more children that are more like the center however that might not happen so here's an example where that didn't really happen here you have two british people who had children and they're fairly medium colored skin right and they had fraternal twins and notice here the fraternal twins they really don't look anything alike in terms of skin color hair color and eye color what they end up getting was kind of near the ends of this spectrum here so it's kind of interesting i've i've talked to students i had a student uh about three semesters ago and she said she's a filipina and she has three children and of the three children one of them pretty much looks like her in terms of skin color and then the other two are much more fair than she is and so um people would consistently say oh how sweet are you the nanny of these other two children and then this is your kid and she'd be like no these are all three my children if you can imagine that so people get to be quite insensitive when they start talking about your children is it's kind of crazy um and unfortunately that can happen socially a lot it's it's a horrible thing and that's what happened to this particular family um that people were constantly saying it was impossible for her to have had these children with him and it just really worked at their relationship and unfortunately they ended up getting divorced if people only understood genetics then they wouldn't be thinking or saying the kind of things that they say sometimes anyway um so much for that right so an interesting topic of looking at polygenic inheritance here is another example of polygenetic inheritance hopefully you remember when i was talking about doing the test cross and while i was telling you about the test cross i was talking about one gene but we know now that eye color is actually polygenic so remember we saw this picture where we were looking at um this person and that happened to be my husband and then my eye and then our two children and here we are when they were much littler right but you can see that um it's a little more complex than that because i mean even though we all have blue eyes they're kind of different colors but the one that's most interesting is my husband who has brown green eyes i mean his base color is brown which is where it comes from but he definitely has that hazel component right so taking a look at it what's happening here is if you look at eye color it's also a good example of polygenic inheritance here are people with blue eyes and they all look different and people with green to brownish color to very very dark and you've probably seen people with super dark eyes that it's really amazing that they look like they only have a black pupil it's really uh really striking looking in any case what we do know about this is that the overall eye color is coated by three or more genes that we know about three for sure but maybe up to 16. remember when we're coding genes what we're coding for our proteins and the protein we're looking at here is melanin that's what gives us the color of our skin the color of our hair and the color of our eyes and so that's why we end up talking about it with multiple genes here because we've got multiple pigments that we're talking about so there's one gene on chromosome 15. this is the main one the one i was kind of kidding about when i was talking about the test cross with my family that's about brown versus blue that's the main one so that means a lot of melanin versus a little melanin okay so um then you have another gene on chromosome 19 which is about green versus blue so green is a lot of melanin relatively or blue is a little bit of melanin so if that person ever says to you you've got brown eyes and your significant other has green eyes you could never have a blue-eyed child well they don't know their genetics because they can if you look at it and you pull out a punnett square and you work through it you can see that a quarter of the time that's possible so don't let people get at you just allow them to move along maybe unintentionally ignorant maybe sometimes mean way in any case so you know it can happen even if either parent isn't necessarily blue-eyed it can happen now looking at this in addition to those genes that i mentioned there's a third one called the okay gene oka two gene on chromosome 15 and that's going to help you with determining how much more pigment so say for instance the person is looking at brown eyes so these are all kind of brown eyes this one says the okay says lay down more pigment that's how you get it darker versus less pigment here you know and that's how you end up getting those differences then you probably also notice that eye color can change with i with age of the person so my grandmother and grandfather uh were both very dark-eyed people and and by the time my grandmother got to be really probably in her 70s or 80s she lived until she was 94. her eyes were almost this kind of orange color that you can see on here and what's happening is the brown pigment is degrading over time and so it it's not replaced as quickly as it as you know you'd expect as you're getting older as you were when you're younger and then the eyes look lighter so people always ask me this question well what about when i wear a certain outfit why is it that my eyes look green or my eyes look more blue or more brown um well this is kind of an interesting thing because it's a matter of a couple things going on number one is perception and number two is uh what's happening with the light remember the pigments that you got are the pigments that you got those the proteins that you have and just because you decide to put on a green sweater that day doesn't mean your pigments are going to change your proteins don't just say i'm going to be a green protein now no that doesn't happen but what does happen is say for instance if this person right here has a slight bit of green inside um and then they decide to wear a green sweater then people will look at it and observe it and say wow your eyes look really green today because they can pick out that color um or say for instance if you're you know wearing a gold color they're going to pick out the gold colors of a brown eyed person or that you know that kind of thing if you're a blue eyed person you often you wear something that's kind of gray and people say wow your eyes look really gray or if you wear something that's very blue also the opposite effect can happen so and the people who do eye makeup really know this well so a person who has blue eyes might wear brown eyeshadow to contrast so that way it'll look much more blue because you're contrasting the brown and then the blue here um and then the opposite can happen with somebody who's brown eyed they can put a slight bit of blue on and then that will kind of bring out the brown and their eyes even more and make them look bigger that way so it's not that our eyes actually change color it might look different in a different lighting because we know about reflecting light and so forth but they're not actually changing color they're not changing their pigments around but our perception is changing that's pretty interesting stuff so some other examples of polygenic inheritance uh height as i mentioned already it's multiple genes that are going to be involved weight iq hair color let me give you an example of say height so we've already talked about how multiple genes can be associated with this right or iq and hair color but let's see don't forget not only is this a result of your genes but it's also affected by the environment let me give you a couple of examples when i was in germany as i said i was a very relatively kind of short woman i was kind of medium to short um but my uh the family that i lived with you know the father was i think um six foot two the mom was like five foot ten and um their children were extraordinarily tall six foot eight and six foot seven and they were in there early they could have still grown more because they think they were like 17 and 19 or something like that and in any case um you know what could um give you that kind of example well it turns out that if you think about it that the two parents um were children um especially the father because he's a little bit older was a child of world war ii and unfortunately um in his particular situation he was the son of somebody who was in the nazi regime yeah which is kind of weird for him to admit it was really something he couldn't understand but his um father died when this man was four years old in any case so rough times right in in a war situation despite that he grew to six foot two now you take a look at his children and they're living in germany which has wonderful medicine it has really good quality food um in general a healthy environment and now they could grow to their potential height and it's very likely that the father and the mother because of the error that they grew up in they could have gotten taller they just didn't have the same kind of adequate nutrition that they would have as their children did another example maybe iq is a little bit contentious of a topic but if you can imagine that a child that is not getting adequate nutrition might not get to their potential iq or whatever measurement you want to have of intelligence because their brains can't develop typically so there's all kinds of examples where you have that environment that's affecting it as well um so don't forget that next thing i'd like to look at is x linkage or sex linkage and they're called this because they're found on the x chromosome okay most of the time i should say so an x uh an x linkage would be found usually a sex linkage you're usually found on the x chromosome okay so remember we've talked about this before that all of these other ones whoops over here are called autosomes okay 1 through 22 and then this other last pair is the sex chromosome right and so looking at that we're going to see that well aside of having to do with the sex of the individual there are other genes on there i mean it's a pretty big chromosome right so taking a look at this here um the first example of a sex linkage or x linkage is just the basic sex determination so when you inherit two x's there's a female when you inherit an x and a y you've got a male and although remember this is a much more complex matter that we've talked about before because we've talked about examples of people who have klinefelter syndrome and all of that too now taking a look at x-linked genes we often refer to them as that because they're any gene located really on the x chromosome although a sex-linked gene could be on the x and or the y okay so what we're talking about specifically is sex-linked genes on either one of these and we'll see why x-linked genes is also very commonly used so an x chromosome has a whole lot more genes than the y you can see all this teeny teeny teeny little dna that's wrapped around coiled around coiled around coiled around to make this wonderful chromosome right here look at how much bigger it is so of course this is a replicated form and this is also a replicated form for the y now there's a lot whoops there's a lot of disorders and interesting kinds of examples of of what has been inherited on the x chromosome hemophilia we talked about um as our example and then there's a number of other examples um that we'll take a look at now first of all remember what we're looking at with the x and y chromosome is on here there is enough length essentially to have more um genes on the x chromosome than the y on the y chromosome there is a particularly important gene and that is the testes determining factor this is kind of funny to think about this because when a baby is in utero they have um the sex organs the gonads which will become either testes or ovaries but they haven't been determined yet if there is testes determining factor at a certain point that turns on and then that tells the body to move these organs outside of the body and then start making them into testes whereas without that it'll go a different direction and be more like ovaries at that point there's another really important gene that's found on the y chromosome and that is whether or not you have hairy earlobes you've probably seen this before maybe not if not you should look it up online because a lot of guys who get hairy earlobes just kind of shave it along with the rest of it but i've seen this picture of this guy who has the world's longest hairy earlobes that he could take and he could actually braid behind his head and they were so long it was crazy anyway so those are um the two genes that are very important on there now x chromosome has 150 million base pairs which is about 1400 genes and the y chromosome has about um 50 million base pairs with about 200 genes but as i mentioned to you these are the two most important ones so looking at this here take a moment and try to figure out what number or letter do you see written in this circle it should be the one that's most obvious to you when you look at it for most people they're gonna see number seven this is the kind of test that we do for red green color blindness um and this is a pretty straightforward one um now here's one where it's a little more confusing to some people what number or letters do you see written in this circle and you have to kind of go with well what do i see first what is most prevalent for some people that's going to be 29 for some people that's going to be 70. for some people they can't see this difference at all and then finally here looking at this one there's another example try to find a dog a boat a balloon or a car as shown in the below demonstration card for people who are uh colorblind especially red green colorblind this is a very difficult task so i don't know about you but i could see bee in this one you can see that boat here if not perhaps you'd experience a kind of color blindness this is exactly the reason why they make traffic lights in a red yellow green in that particular order always in the united states so people who are driving around can see the intensity of the light but not necessarily the color it's a little bit different when you go to different countries though so then you have to relearn what's going on now finally i want to talk about environmental impact on gene expression here's a kind of an interesting example where you have um two of the same plant these are hydrangea this one has been planted in basic soil and it makes the flowers turn pink however when you take the same plant and you put it into acidic soil like with these pine needles you end up getting a blue flowering plant really interesting that that can have an impact on gene expression here's another one as well where these two bunnies were maybe littermates but at the same time depending on what temperature they're raised at you end up getting this tipping as it were they call that if they were raised in a cooler temperature they have the tipping if they're raised in a warmer temperature then they don't have that and then finally we know that there can be differences even among twins based on what they their environment was did they get adequate food do they live more in the sunlight do they get more exercise do they get less exercise do they get quality food all of those kinds of things will affect gene expression all right now um i'm going to go ahead and show one more thing in just a moment but this is the end of this section the last thing that i wanted to show you before we move on for today's recording here is just kind of what you've learned already and how much you're familiar with things and then show much how much there is still to learn it makes science very exciting and very interesting let's take a look at this video and see how much of it you're familiar with and then see what parts that you haven't learned about yet so i'm going to go ahead and share my computer sound here hopefully it will work if not let me know and i will share you the website with you okay i hope you enjoy the song to make one me you just add a half of mom and half of dad that is what i once believed but now i know that i was wrong you gave so much to me mom besides one half a set of genes you gave me nutrients transcription factors nearly everything that matters plus my prenatal environment transplacental inheritance mrna mitochondria that back in the day once belonged to societal i just want to thank you for supplying them just like two strands of dna are spirally entwined your nature and your nurture inspiringly combined scientists true slightly more than half of everything i am his thanks to you slightly more than half of everything i am is thanks to you mitochondria power the cell and they have dna as well transcription factors modulate transcription and since they're in the cytoplasm the egg's the only one who has them in sperm i guess they don't have the ambition my sex determination gene means that i'm a guy you gave me [Music] that's why slightly more than half of everything i am is thanks to you might be more than half of everything i am i took your blood and sucked it dry gross but true sometimes i wonder where the time went where did it go sometimes i wonder where it all [Music] never is all you have done for me i'm not that since you paid for college i'll get my bs degree of science but absolutely true slightly more than half of everything i am is thanks to you more than half of everything i am is thanks to you you gave me nutrients transcription factors nearly everything that matters mrna mitochondria that back in the day once belonged to you nutrients transcription factors everything that really matters mrna mitochondria that back in the day once belonged to uh [Music] [Applause] scientists remind me slightly more than half of me is thanks to you oh and by the way dad right all right i hope you enjoyed that song um and uh i will be talking to you later i hope you have a good evening bye