DNA, Chromosomes and Genes

so in this video we're going to talk about DNA chromosomes and genes first thing we're going to need to do is recap DNA so if you haven't already I really recommend you go and watch my body's DNA video and you can do that by clicking here ok so let's do this DNA recap right in the DNA video we went through the main points and features of our DNA molecule and we found that they were these points here first of all DNA is two complementary strands we call it a double helix it's like that ladder which has been twisted up it has a sugar phosphate backbone it's made up of four types of nucleotides a is the base on one nucleotide T is the base on another C and G so there are four bases on those nucleotides we have complementary base pairing in DNA it's a rule where a always pairs with T and C always pairs with G DNA is the genetic information of living things and DNA is able to self replicate just to remind ourselves let's bring in this molecule here so here's our DNA double helix sugar phosphate backbone sugar phosphate backbone these are the bases which are part of the nucleotide but we have a T C and G and they always pair up in a complementary manner a and T a and T and T C and G C and G C and G C and G so that's our DNA recap so what are chromosomes well I'm fairly sure you've heard of them before and it might be certain bits and pieces which you've heard about a chromosome for example you might have heard that humans have 46 chromosomes you might have known that crome have something to do with DNA let's just bring this in here this is the human karyotype is that there's that word here which you can hopefully make out karyotype a karyotype is a picture of all of the chromosomes from within a cell of a particular species and this is the karyotype for humans so in the human karyotype as you can see we have 23 pairs of chromosomes which make up 46 and that's something you may or may not have already known humans have 46 of these things called chromosomes but as we said what are they well let's summarize the key points about chromosomes so here they are okay guys first of all chromosomes are long threads of DNA and in some instances like in eukaryotic cells protein as well more on that later chromosomes carry genetic information of a cell and that's you might be thinking of course because they're made of DNA and DNA carries genetic information well then obviously if chromosomes are made of DNA then they to carry genetic information groups carry genetic information of a cell the information determines what proteins are made so that is what the information is for it determines what proteins are made and they're made up of many genes something else that we're going to talk about genes coming up soon so they're the main points about chromosomes so let's have a look at an overall picture of what we're talking and what we're dealing with you all right here we got a cell we're well familiar with selves now you be recognizing this is a eukaryotic cell and that's because it has a nucleus now within the nucleus we find chromosomes however you might be wondering why is this chromosome in an X shape we're the ones that brought in before these ones here these weren't in act shapes these were just one linear component the reason for that is because this is an example of a chromosome where the DNA is already undergone replication and the cell is about to divide so that's a key difference and there'll be more on that at another time so here we have the chromosome and then if we break the chromosome down and look into and zoom in a bit further we can see that the chromosome is actually made of roundup molecules of DNA so here we have it here that the molecule we've learnt about made of a double helix of nucleotides all bound together sugar phosphate backbone and all of our A's T c's and g's in a eukaryotic cell that DNA gets welled up and wrapped around these proteins they're called histones wrapped around these proteins and packaged up into a big condensed chromosome so that's where DNA fits into this conversation okay cool so what a genes right that's the final piece of this puzzle where does this idea fit again I'm sure it's something that you've heard of before genes we know when we have attributes and characteristics that we've got from our parents it's got something to do with genes what are they where they fit in this conversation well here's your definition genes are segments of chromosomes that contain the code required to direct the manufacture of a polypeptide or an RNA molecule let's just take a deep breath because that is a big statement right let's just go over it again genes are segments of chromosomes that contain the code required to direct the manufacture of a polypeptide or RNA molecule so they've got the code that cells need in order to tell them how to polypeptides or RNA molecules I'm going to go into this process of how polypeptides and RNA molecules are made from genes in videos on transcription and translation they are part of what we call protein synthesis and there's lots of information to go through there and we can learn more about that in those videos okay back to our overall diagram here where we had our cell eukaryotic because it's got a nucleus it's got the chromosomes ah another point I didn't make before because this is eukaryotic the chromosomes are in fact linear in a prokaryotic cell not only would we not have a nucleus but we also would not have linear chromosomes we would have in fact circular chromosomes and we wouldn't be using proteins to make those chromosomes the chromosomes in prokaryotic cells only consists of DNA so in our general diagram we worked out that the chromosomes are in the nucleus the chromosomes are made of Discworld up and condensed DNA but if we look down at our DNA here DNA and sections of the DNA our genes and here we have an example of a gene really though we got to be careful this is just a small section of the gene because this is only about six or seven base pairs long in reality guys genes are hundreds of base pairs long so not very realistic here but that's just showing you a section of a gene and it should help you to see when genes fit into DNA and chromosomes another way that we can look at it is using this diagram okay in this diagram we have our chromosome again this is a chromosome where the DNA has already replicated it's ready for cell division it's joined to sister chromatids which are identical versions of the same chromosome and they're joined at a centromere to make a single chromosome that's going to go through cell division don't freak out there will be more on that in another video so here DNA is making up this chromosome and sections of that DNA are called genes and the genes are made up of these base pair repeats and those base repeats are the code that are going to direct the manufacture of polypeptides or RNA molecules again this here is only a short section of a gene because in reality genes are hundreds of base pairs long but this is just a good way of showing you where a gene fits into this DNA molecule and where this DNA molecule fits into this chromosome so let's bring back our human karyotype 23 pairs of chromosomes to make 46 chromosomes in a human cell just a side note if you look down here you can tell the gender of this human this is a male because these are the sex chromosomes and males have One X chromosome and one Y chromosome notice they're the only two that don't look identical to each other like all of the rest all of the rest are identical pairs in males in the sex chromosomes they have one X and one Y in females they have two x chromosomes so 23 pairs of chromosomes make up our human karyotype now I need to tell you about the human genome project it's a fantastic initiative that has helped us to learn so much information about human DNA and what we know currently our best research at the moment tells us that there are approximately 20,000 human genes now if we think about it they're spread across 23 pairs of chromosomes 20,000 genes 23 pairs of chromosomes we've come to the conclusion that there are lots and lots of genes on a chromosome so we know there are many genes per chromosome and the other thing that we've learned is that chromosomes can be identified based on the genes that they contain if I show you what I mean there I can do that by bringing in two of our chromosomes these this is human chromosome seven and this is human chromosome four its easiest to locate genes when something goes wrong with them so some of the easiest genes to locate were genes like the Cystic Fibrosis gene that's located here on chromosome 7 and the Huntington's disease gene is located here on chromosome 4 so we can identify a chromosome based on finding those genes and their locations so I was talking about the human genome project before the human genome project has been responsible for finding the base sequence of all 23 human chromosomes which means we know the base sequence of all of these things here now the challenge at hand is to work out what all of this information means and where each gene is located because an interesting fact is that most of a chromosome is actually made up of non-coding regions of DNA and the actual genes only account for a small portion of chromosomes so another challenge is working out well what is this non-coding DNA for and that's where in biological discovery it's exciting times hopefully it might inspire you to do some further study into biology that's it for this video looked at the relationship between DNA chromosomes and genes I really hope it helps thanks for watching and we'll see you next time yeah

Channel: Jeremy LeCornu

Views: 243,072

Keywords: DNA, Chromosome, Gene, Genes, Biology, Cells, Macromolecules, macromolecule, nucleotide, protein, nucleus, code, science, education, anytimeeducation

Id: z8ojaHrxQR0

Length: 13min 30sec (810 seconds)

Published: Sun Sep 14 2014