Transcript for:
Overview of DNA, Genome, and Inheritance

hello good afternoon and i hope you're ready for the web class today so in today's uh live web class we're going to be looking at dna the genome and inheritance so um let's see who's arriving and see who is going to be joining us so i'll give us a few minutes while people join in it always takes a little while for people to join us and then we will start the web class so i hope you're all having a good summer holiday um a little bit left of it now hello khadijah hello good to see you where are you from hopefully everybody will be joining us in a minute and then we can get on hello hi hello oh we're getting quite a few people now managing to get on where's everybody from from birmingham excellent that's just near me i'm just just around the corner from birmingham so where else is everybody else from let's have a look uk yeah whereabouts in the uk okay yeah brilliant so hopefully everybody's having a good time and ready to do some learning ready to get back to school and to get back to classes yeah southwest oh lovely hopefully the weather's good down there brilliant all right where else we've got sully hole another one near me there we go just down the road from me although we're just about to move to the cotswolds this coming week so that's quite exciting so when do you all go back to school i should think that's quite soon isn't it in the next couple of weeks those who are in scotland are already back egypt oh lovely i love egypt i have been quite a few times to egypt it's lovely seventh yeah that seems like a good time to be going back gives you another couple of weeks doesn't it which is great right while the last few people are joining us yeah 7th of september another one for 7th of september um i will start sharing my screen so you can all see what's going on ready for the web class botswana i love botswana i have been to botswana fango delta it's fascinating all right let's have a look then ah so hopefully you can all hear me and you can see that quite well sixth septum hello hi yeah brilliant namibia wow there's a lot of people coming from africa that's lovely to see i have not been to namibia but i really want to go to namibia it's one of my places on my bucket list of places to go so let's have a look at our biology web class today gcse biology webclass getting you warmed up ready for your return to school and we're looking at dna the genome and inheritance today and some people get these a little bit confused some people really enjoy them um we'll have a look and see how much you know but try to be as interactive with me as possible through the chat because the more you interact the more you're going to get out of it all right so that'll be libya wow and sri lanka wow fantastic some great countries here right so let's have a look first of all i'll introduce you in case you haven't uh seen any of my web classes before um i'm philippa and i'm the lead gcse biology teacher um with my qualifications i've got a bsc in animal science from leeds university and i did pgce in biology and games also at leeds um i'm a teacher and a head of biology with over 25 years of experience and hopefully you'll find that i'm really enthusiastic about biology as well so let's have a look yes so the objectives today then what we are looking at in today's lesson so we're going to describe the structure of dna as a polymer and define the genome so what the genome is we're going to discuss the importance of understanding the human genome oh the philippines somebody wow that's fantastic um i don't think we've had somebody in one of my lessons from philippines there we go um and oh yeah that's fantastic i'm really pleased that you're wanting to gain knowledge um at such an early stage in your in your education but hopefully this is going to help you isn't it bridge any gaps that you might come across stretch yourself so we're going to explain the role of alleles genotypes and phenotypes and the inheritance of characteristics what i'm not going to go through today are punnett squares and family trees they will be covered in another lesson transcription and translation which is all about the dna itself and and using the codes and mutations and gene expressions so we're going to stick to the basis of the uh genetics today just the basic information about dna and phenotypes and genotypes now from china year nine yeah gaining knowledge fantastic zimbabwe wow another fantastic country some really interesting places here right so we need to look at the specification points don't we so obviously we tried to cover as much of the specification as possible for all of the boards so first of all with aqa hello hi zara nice to see you okay ah you are zara in your sister's account fantastic and hi from pakistan hello everybody so aqa those people are doing aqa it comes under dna in the genome and genetic inheritance so um you're going to be looking at various different parts of these two sections of the specification so you're going to be looking at the structure of dna in the genome the importance of the genome um and what um the genotype and phenotypes are so we're going to look at those we're going to look at dominant and recessive alleles as well so we'll be looking at that then we're going to be looking for ocr those people who are doing ocr because i'm not sure what all of you are doing ah from spain hello from spec to spain um with ocr we're going to describe the structure of dna again um and the some of the key terms that we're going to be looking at today and we're going to be looking at how genes um pass on the information to offspring aqa right it's quite there's quite often a lot of people in aqa what other um boards are we doing here aqa aqa seems to be quite a popular one so that's ocr and then of course there is edxl as well so edexcel describing dna is a polymer um we're going to be looking at the genome the importance of the human genome the differences in inherited characteristics and alleles and dominant and recessive alleles and phenotypes and genotypes and excel right okay so we've got some aqa and edxl people here but it should cover most of what is needed um for all of your exam board so that's the good thing about these web classes all right so let's have a look what do you actually know so far so if we started off with a cell what is the next stage down from the cell where we so what is the nucleus of a cell so a cell is bigger than a nucleus what do we find inside the nucleus hi nuru from kenya so inside a cell so you've got a cell like this and then you've got a nucleus in it what do we find yes chromosomes so in the nucleus we find chromosomes and what are chromosomes made up of brilliant well done dna okay so chromosomes are made up of dna and what do we find the specific sections of dna that actually code for protein do we know what those are called they're the bits on the dna that we're really interested in because they do the coding for the protein so one section ah codon yeah codons which make up the gene good so genes which are made up of codons which then code for the amino acids on the proteins don't they so we have the cell the nucleus and in the nucleus we have chromosomes and they're made of dna and the dna is broken up into sections called genes and each gene codes for one particular protein so genetic inheritance where do we get our genetic information from what makes us who we are does anybody know yeah deoxyribonucleic acid fantastic whoever managed to get that one down for dna that's really good so what do we already know about genetic inheritance where do we get it from our parents excellent and does any one parent give more of the genetic information or is it a fair split yeah we get it from our parents 50 from each side brilliant so half of the genetic material yeah from each parent excellent so that's why we often look like a complete mix of our parents doesn't always happen like that but we do tend to look like a a mix of our parents don't we so he might have you know the eyes of a mom and the forehead shape of your father or something like that adenine thyme inside singuanin yes excellent so those are what give us the code in the dna aren't they okay so those the bases that we find in dna which give us our codons well done yeah a lot of you oh you have a genetic heart condition well isn't that interesting so did you get that passed on from one of your parents that you're okay well i'm glad to hear that yeah there's a lot of genetic um you know diseases and things that can be passed on can't there so um yeah well that's really interesting so let's now that we've looked at what we already know should we now move on to actually looking at a little bit more detail of the dna and the genome so this is a cell obviously so this part is the cell what's this that it's pointing to we've just talked about it this arrow here so this is where all of our dna is found so obviously the nucleus good do be careful spelling the nucleus some people struggle with the the term nucleus to spell it so it's the nucleus and obviously in the nucleus we have our oh hypotropic part yeah cardiomyopathy i was just doing that with my um daughter because she's doing her medical exams so there we go yeah this is the nuclear membrane here isn't it this is the nuclear membrane and then inside the nucleus we have our chromosomes don't we so this is a chromosome and chromosome basically means colored body so basically we can stain them so we can see them and that's what chromosome means a colored body um and then of course we have the next section down here which is what the chromosomes are made up of which you've all been telling me already which is our dna isn't it deoxyribonucleic acid as one of you so correctly put and then we've got our section which codes for a protein which is this bit up here what's this bit again the section of dna that codes for a protein yeah this is the double helix isn't it because it's two strands wound round each other and this is the gene and one gene codes for one protein brilliant and so does anybody know how many chromosomes human cells have in them the normal human body cells does anybody know oh wow lydia that's really i'm very very sad but they're learning so much more about it aren't they 46 brilliant so 46 chromosomes so in a normal human cell we have 46 chromosomes and that's a lot of dna it carries a lot of genes as you can imagine all right so let's have a look a little bit more detail at dna and genes so what is dna we know it's a strand that and it had formed a double helix didn't it but what is dna does anybody know how to describe it tell me anything you can to describe dna yeah we've got 46 chromosomes so 46 chromosomes in our cell all of our chromosomes are made of dna what is dna can anybody describe what dna is it's a nucleic acid super so it's a chemical which is known as a nucleic acid well done super and it's used yet it's a poly nucleotide excellent a poly nucleotide because it's lots of nucleotides joined together fantastic it makes you different stores genetic yeah and it's deoxyribonucleic acid fantastic and so if it's a polynucleotide that means it's a polymer which means it's made of lots of repeating units and how many strands are there somebody talked about a double helix how many strands are there wound together it is a very complex molecule there's lots of stretches of it yes brilliant so it's polymer made of two strands wound around each other in a double helix so it's two strands double helix means it's two strands wound around each other in a helical structure okay that's discovered by watson and crick um so it was really interesting that they discovered that in the 1950s the structure of dna yeah so it's two strands there's one strand there's another and actually it looks like a spiral staircase because what it looks like these are like the handles that you hold on to and these are where you put your feet okay the bars across so it looks like a spiraling staircase all right and that's how i always remember it yeah so it's double stranded dna single stranded rna so dna is a double stranded all right and rna tends to be single stranded yeah brilliant so here we have our dna it's the double helix so it's got the two strands wound around each other in this sort of spiral staircase so it's just it's kind of like a ladder which has been twisted and you've got these bars across which are basically the bases that are joined together and those are like yours your rungs up the ladder and then the side bits um are the bits that you hold onto as you go up a ladder all right um and that's made up of a deoxyribose sugar and phosphate groups form this part and then we've got the um the nitrogenous bases form those rungs all right so a one gene codes for what yeah fruit flies only have eight chromosomes you're absolutely right and it's just that it's dna is normally double-stranded and rna is normally single-stranded that's all that's what we tend to um go for oh the fruit flies are really interesting because there's been a lot of genetic experiments with fruit flies they're very very useful for doing genetic inheritance experiments the fruit flies so there we go so one gene one gene codes for one protein and here's a protein made up of lots of different amino acids so those are amino acids joined together all right and somebody mentioned a codon one codon codes for one protein but we're not going to go into that in detail today okay now um the dna is made up of lots of individual nucleotides so a polynucleotide means that it's made up of lots of individual nucleotides all right and nucleotides basically if you're interested look a bit like this it's like a house with a garage with a satellite dish on and this is the deoxyribose this is a phosphate and this is the nitrogenous base and somebody mentioned about adenine thymine guanine and cytosine and that's what the nitrogenous bases are all right so yeah we do get our amino acids from our food so we consume protein break it down absorb it in our digestive system it goes into our blood and then we build it up into new proteins all right so that's called assimilation so we get the protein we digest it in our digestive tract then it's small enough the amino acids are small enough to pass into our blood from our digestive tract and then we build those up depending on the code from the from our dna um it determines which order those amino acids are built up so that's a really good question and yes one codon codes for one amino acid okay any other questions we were happy with that great stuff so let's have a look at the next part then and the genome the human genome which was um which was discovered by um scientists all over the world work together to to to discover the human genome because it's really really important um because as soon as we know about the human genome um which is the whole genetic material of an organism so we know every single code for every single gene of the human genetic material all right it means that we can use this for so many useful things all right so it's really helped with our development in treating genetic diseases and um developing personalized medicines which is a really um forward thinking part of medicine now all right ah right please explain one amino acid case right yeah one codon is made up of three nitrogenous spaces so we've got the adenine diamine guanine and cytosine all right there's four of them but they work in threes which is known as a codon and three nitrogenous bases code for one amino acid all right so hopefully that makes sense all right um not that we're going into that in a lot of detail but if you're asking i'll explain it so yeah three nitrogenous bases either adenine guanine cytosine or thymine whatever order they go into that's one codon and that codes for an amino acid okay right so human history so we can look at where we can trace back migration patterns and look at where people have um come from which continents they have moved from and so we can see evolutionary history we can see how humans have developed over time by looking at dna so we can trace migration patterns and see how where people's origins are from and also evolutionary history so we can see how humans have developed which is really interesting and very useful to find out more about evolution if two codons are the same they're going to code for two same amino acids next to them okay ah yes now you're talking about the pairing in the actual um helix but it that doesn't link into the codons all right that just holds the helices together so adenine pairs with thymine cytosine with waning but that just holds the helix together all right that isn't actually to do with the codons if that makes sense uracil is to do with rna all right so going back to the genome then we can trace migration patterns in evolutionary history and we can identify genetic disorders so people who have got if there's some a really serious genetic disorder within a family that is going to cause such deformity that the child is going to possibly die before it's born it can be identified all right and um also genetic diseases can be discovered in fetuses before they're born so they can be ready to treat them as soon as they're born as well okay so genetic disorders you could identify them and that's really important because it means that they can look at research into it how they can improve it and treat them so that's really useful for looking and so cystic fibrosis for example they are developing treatment for cystic fibrosis which is a genetic disease another one which is really interesting is like i said this personalized medicine where they're actually realizing i don't know whether any of you have read it in the news but um they're trying they're finding that certain drugs work better depending on your genetics so when people for example go and get treated for cancer they will actually choose the medicines depending on what your genetics are because different chemotherapies and other medicines work better for different genetic makeups so that's really interesting as well all right so uh we can have genetic cures and drugs tailored to people's genomes and this is just developing more and more it's fascinating to see how that side is developing you may also also have heard about genetic disorders such as people who are prone to maybe serious aggressive breast cancer they may have their breasts moved before they actually get breast cancer they might choose elect to try to avoid that all right so there's that as well brilliant okay so the other thing is um genetic counseling can be um really important that people may know that there is a serious um genetic disease in their family and some of the children might decide they want to find out whether they are prone to it others might decide that actually i'd rather not know because they don't want to have that sort of the if they do test positive for it that that's them worrying about it for the rest of their lives so genetic counseling is when people are they go in and they discuss it with the specialist and they discuss about what the options are whether it's a good idea to be tested for it and then also how they can manage it if they do test positive for this particular genetic disease so genetic counseling predict the risk oh has it that's really strange okay i'll try to write um further over i don't really know why that has moved over so i'll try to keep over to the left a bit thank you for letting me know about that so predict the risk of developing diseases and so they're talked through the problems that they might come across um so that's tailored to genomes and it's genetic cures and drugs there we go so at least that all comes onto the screen then thank you yeah the so genetic counseling is really important it's very very useful um so they know what the risks are and what can be done to help you all right so this is i hope you're finding this really interesting it's a really interesting topic so how confident are you feeling at the moment do we think it's straightforward all right super confused what do you reckon one two or three just drop down one two or three for me so that i can see how you're feeling brilliant okay yeah some of it's quite new to some of you some of you have come across it before so okay good so we're not going any further down than twos at the moment so there is a little bit to learn isn't there but yeah do ask questions as we go along so if there's anything you're unsure about that would be fantastic good brilliant so ones and twos all right brilliant okay so let's have a look this is a two mark question that we're going to be looking at so as the broad beam germinates each new cell has 12 chromosomes in its nucleus explain why a broad beam seedling needs chromosomes so what do chromosomes carry to start off with what do we find on the chromosomes we've talked about this and we've done the flow chart haven't we so what do we find on chromosomes oh it's your first time to this topic well hopefully we're not confusing you too much because there's lots of people some some people have done this before obviously and some people are completely new to it so yes chromosomes are made of dna and what are those short sections of dna that carry yeah genes so we need to carry genes because the genes code for protein which control our characteristics yeah yeah they're needed to make proteins which obviously control the characteristics of the plants whether it's going to grow tall or characteristics i'm trying to spell there we go i had to think then so 46 chromosomes are needed in humans they're all different living organisms have a different number all right so all different living organisms have different numbers of chromosomes so we have 46 which is quite a lot broad beans have 12 um and so on so there's lots of different numbers of chromosomes happy with that so that is a foundation tear question from edexcel all right yeah so well the genes will determine because some broad beam plants will be dwarf broad bean plants some will be tall ones depending on where they grow so um the genes will determine how tall it's going to grow all right just like our genes determine on how tall we're going to be and that of course we get from our parents right let's have a look at this one another two marker state two ways that the human genome project has been used to improve medical science so what has been the benefits of the human genome project so if you are tackling an exam question it's a really good idea to have a highlighter available so that you can highlight those important points so that you are keeping yourself focused on what you're trying um to answer all right so anybody got any idea can we remember what we were talking about with that human genome project can anybody come up with anything can anybody remember what we were talking about what have we got to have scientists detect yes certain diseases are you confused okay so genetic counseling was one of them wasn't it to help people discover about their genetic diseases there was personalized medicine do you remember that okay so um a better understanding of genetic disorders could be one of them of genetic disorders so we know how we've got more idea on how to treat them genetic counseling good yeah personalized medicines that could be another one i'll just stick that on there so that you've got it personalized medicines could be one good okay um predict the risk of a genetic disorder any of those would be fine as an answer okay so you just need two of those yeah trace migration patterns but it's more to do with medical science with that one um rather than evolution so genetic history yes you can trace that back through your family can't you to look at the risk that you have of getting a genetic disorder maybe all right so the genetic history in a family is really important to see whether you are likely to be at risk of a genetic disease and the personalized medicines of course so important so important such an amazing development at the moment yeah dna identification so you can actually look for that genetic disorder can't you and some can be treated with uh therapy okay so brilliant well done so far now let's have a look at alleles so we're on to our next section of the um lesson the web class so we're going to be looking at alleles and inheritance so alleles if you're looking at alleles um alleles are different types of genes so you could have your eye color gene and that's the type of gene but then you can have blue you can have brown you can have green you can have hazel those are all alleles so alleles are a type of gene all right so they're different types of that particular gene so you have the gene for hair color or eye color or nose shape and then you have the alleles which are the different types of that particular gene does that make sense hopefully you've heard of that before yeah blood type that's another one hair color hair shape height lots of things so chromosomes as we've already talked about chromosomes are inherited from parents aren't they during reproduction i know you probably don't want to think about that but parents in reproduction that is how you have ended up with your genes so we'd already realized that half comes from the father and half from the mother so these are carried in the sex cells or gametes i'm sure you've heard of gametes before which are sex cells what are the sex cells in humans that come from the father what are our gametes what are the male gametes in humans and what are the female gametes yeah brilliant so do we know what the gametes are or the sex cells so sperm brilliant in sperm cells which are the smallest cells in the body and the egg cell or ovum which is the largest cell in the body so you've got the smallest cell with the largest cell okay so they have special nuclei their nuclei only have half the normal number of chromosomes so in a normal human body cell there are 46 chromosomes how many chromosomes are there going to be in a gamete so if there's 46 in a normal body cell yes brilliant so there's 23 fantastic 23 chromosomes in the gametes because half comes from mother half come from father and in fertilization 23 plus 23 the nuclei views in fertilization and we end up with our 46 chromosomes in the body cell brilliant does anybody know the special name for a normal number of chromosomes in a nucleus there's a special name for it there's a special name for the number of chromosomes in a gamete and it means the normal number of of chromosomes and half the normal number of chromosomes does anybody know what they are called haploid super it's a haploid over here i always remember it because h a for half so haploid and diploid good die because they're in pairs diploid die means two so they're in a pair and haploid half for half the normal number of chromosomes super well done so we say that the chromosomes come in pairs because it reminds us that half of from the father half from the mother and we end up with these 23 pairs and each one of the pairs has the same genes on it all right so one particular chromosome will carry eye color one will cut carry nose shape or chin shape or height all right and so therefore they work together in pairs but what happens is we need to talk about how you end up with say your dad has brown eyes and your mum has blue eyes what color eyes do you end up with so this is when we start looking at alleles which are a different type of gene all right different types of gene so here we have um this is the genes what the genes are in your body so if you were talking about what type of genes you have in your body do you know what you would call it whereas this is what you look like it's something type so we have a particular name for something type for jeans and something type for what you look like does anybody know what i'm talking about here what is it yes brilliant well done genotype for genetics that's the genetic makeup brilliant well done and phenotype is what you look like the outward appearance so the genotype might be um blonde hair plus blonde hair alleles and the phenotype would be they look like they've got blonde hair okay it's the actual hair color so we have in a pair of chromosomes okay one from the mother one from the father we end up with two copies of each type of gene so say hair color here all right so here's brown and here's blonde okay and those are both hair color genes but this is the brown allele and this is the blonde allele all right so these are the alleles they are it's like when you go to the supermarket you say all right i need some butter you go down the butter aisle that's like the jeans and then the alleles are your clover and your whatever i can't even think what all the different types of butter are but uh flora and things like that so those would be the alleles hopefully that makes sense so we have each of us have two variants of each of the genes two alleles of each of the genes in our body and they may be the same one so you might get blonde hair from mother and father or you might have brown hair from father blonde hair from mother and then this is where we find out what are we going to end up with as our phenotype one h or two i don't quite understand that last question so explain and i will answer so how do you is this the one h or two okay so um does everybody understand what an allele is then you're happy with what alleles are oh one hour yeah it's a one hour lesson okay one hour web class we'll have another one next month as well which is brilliant so why do we end up looking like we do because we get a mixture of alleles don't we we get one from mother one from far they might both be the same or they might be different so let's have a look at this one when we look at eye color yeah web classes yeah so one hour web classes we do them once a month um and hopefully you find them useful it's always good to do a bit of warming up on your your learning isn't it so we have dominant alleles and we have recessive alleles so if you look around i know your class at school you may notice it there's more people with brown eyes and there are with blue eyes all right and this is because the brown eye allele is a dominant allele which means if the dominant allele is in the pair it will be expressed so it is always expressed even if there is only one copy present all right so here we have and the dominant one is shown by a capital letter because that shows it's dominant so this one is brown eye color over here we have blue eye color which is recessive so if their recessive one is an extra dominant the dominant's always going to overpower it all right the only way the blue can show through is if it has a weaker one so it might be paired up against green or something like that or if there's two blues present so only expressed the recessive is only expressed if two copies are present so recessive alleles are only expressed if two copies are present so here there's a brown and a blue so the one that wins here is brown so this person is going to have brown eyes does that make sense hopefully so what i'm going to ask you to do is we're going to look at three different genotypes all right and we are going to discuss those genotypes and see can we work out what is their phenotype that outward appearance because it's the reason the recessive allele because the dominant one is the one that is going to determine which protein is made in that eye and that's the way it works with the dominant okay so with this one this is known if we look at this one we've got one dominant and one recessive all right so this is known as heterozygous which means there's one of each type if we had two blue eyes this would be homozygous because that means of the same type homo is the same type hetero is different types so homozygous recessive because it's just two all they've got here are the recessive alleles over here if we've got big b big b it would be homozygous dominant because both of them are the dominant allele so we have homozygous dominant homozygous recessive and heterozygous now these are words that people do get confused with so hetero means two different ones homo means are the same so homozygous recessive means both are recessive homozygous dominant means both are dominant and heterozygous means we have one of each so i am now going to show you three different genotypes and we're going to try to work out what's the name of their genotype and what is their phenotype in other words what do they look like okay are we ready for this so let's have a look at the first one here's the first one first of all what is their genotype are they homozygous recessive homozygous dominant or heterozygous so you can put hr for homozygous recessive hd for homozygous dominant or just h for heterozygous what do we think the genotype is h heterozygous straight in nazara brilliant yes well done yes brilliant well done so we've got heterozygous so that is the name of their genotype because they've got one dominant and one recessive one of each brilliant well done you're getting this so what is that outward appearance what color are their eyes what is their phenotype in other words what do we think their phenotype is yes well done so they've got yeah well done brown eyes super excellent work right what about this middle one so here's the mother and the father again what is that alleles here so what alleles have we got on each of these is this first one is this big b or little b i'm pleased that you're getting this so this light blue chromosome what allele is that carrying yeah homozygous dominant genotype brilliant homozygous yeah brilliant dominant because we've got a big b haven't we and a big b so it's homozygous dominant so what's the phenotype in other words what color are their eyes well done you are doing really well all of you this this is fantastic brown eyes brilliant so what have we got at the end then brilliant eye color is brown they both have brown right yeah but it's one person because those chromosomes are in their cells okay so this is one person the chromosome from the father the chromosome from the mother and those in their nucleus have given them brown eyes brilliant so this last one then let's have a look at these alleles what is the phenotype of this last one number three that was number two this is number three oh i'll put three over there so we can see it some reason it's being cut off so what is the genotype of this last person we got any idea what the genotype is of this last person you can put the initials again if you want homozygous recessive written out in full as well brilliant homozygous [Music] recessive because both of them are recessive alleles aren't they so what is the phenotype of this person what color eyes do they have what do we reckon yeah homozygous yeah brilliant well done you're all getting this you've done so well very very impressed this is good work well done everybody so how are we feeling about this how confident are you feeling are you ready to have a go at a couple of exam questions to finish off with just got two exam questions up late yeah it's it it's just trying to show one ellie yeah i know it's because a lot of people draw the chromosomes like that when the cell's actually about to split but yes i understand what you're trying to to say there okay brilliant yeah all happy with that good stuff so the inheritance of sickle cell disease can be represented using big d or little d sickle cell disease or sickle cell anemia is quite a nasty one if they get low in oxygen their red blood cells change shape into sort of a sickle shape like this and it gets stuck in joints and capillaries it's very painful all right so the inheritance of sickle cell disease can be represented using big d or little d use words from the box to complete the following sentences so let's see what we can come up with this i will call number one this is number two and this is number three write down what you think the words are for each of these blanks one two and three so just put the left the number and then put what you think it should be let's see what we can come up with it doesn't matter what order you do them in just go for something genotype brilliant recessive so genotype is correct the alley or little d little d represent the genotype of a person with sickle cell disease the allele little d is recessive and when a person inherits two of these alleles that person is now this is that word that we use if we had little d little d what would we call it we've just been doing this with the eye color all right and when a person inherits two of these alleles so they've they've inherited two recessive ones what's that good homozygous so obviously we would call it homozygous recessive but they haven't got that choice we've got homozygous brilliant well done good work so the last question then let's have a look at this one phenylketonuria pku is an inherited condition it makes people ill pku is caused by recessive allele what is an allele what do we think we can use as a definition for an allele can you remember what i talked about this is just one mark can anybody tell me what they think an allele is even if you just put it in your own words yeah we get them from our parents so we get our genes from our parents don't we and each type of gene has a form of yeah yeah it makes up the genotype so it's one form of a gene isn't it basically so you can have the gene for eye color and then you could have blue brown turquoise whatever all right so well done so it's one form of a gene all right um what is meant by recessive an iso form of the gene is called allele very good i like that one so what is meant by recessive when do we only get that expressed in the phenotype what has to be the situation for a recessive allele to be expressed in the phenotype remember brilliant only expressed if two copies are present brilliant so if a dominant is present it's not going to get expressed isn't it because the dominant will override it super work well done you've done really well so hopefully at the end of this lesson you can now describe the structure of dna as a polymer and it's that double helix isn't it that looks a bit like a stepladder which is twisted around and the genome the human genome is the whole genetic makeup of humans the importance of the human genome with personalized medicines being able to um understand more about genetic diseases and predict whether somebody's like to get here and genetic counseling and also looking at the evolutionary history and we should be able to explain the role of alleles the genotype the phenotype in inheritance of characteristics hopefully you've all enjoyed that and found it interesting has anybody got any questions last questions for me and don't forget there are upcoming web classes again all right so we've got more upcoming web classes coming i'm glad you've enjoyed it hopefully you've all understood some a little bit more about this topic i find it fascinating and then yeah if you look at the chat now it's got the youtube schedule on it so that you can tap into that all right right brilliant and don't forget you can always go back to this class on youtube because it will be saved on youtube so you can always review back over if there's anything you're unsure of all right so take care everybody and it was great to see you all all right bye bye my pleasure see you soon bye