[Music] in this video we'll be starting with the chapter of DNA now this chapter is found in paper 2 and it consists of around 27 marks when you study remember have your exam guidelines with you always as they will tell you exactly what you need to study so that you don't study any unnecessary work now according to our exam guideline we need to know the general cell structure with an emphasis on the ribosomes cytoplasm and in certain parts of the nucleus we need to know that there are two types of nucleic acids DNA and RNA and then they consists of nucleotides now looking at the ribosome these structures should not be or these organelles should not be strange to you as you've done quite a lot of this in great thing so this diagram on the left here is a general structure of a cell that you would find an animal cell you've got the the basics like the mitochondria the vacuoles the centrosomes all of those things that you would find in itself now looking at the ribosome the function of the ribosome is that it is responsible for protein synthesis now synthesis means to make or produce so in this case protein production to make proteins and the general structure of the ribosome is as on this diagram on the right hand side it has two units a large subunit and then a smaller eye sorry a lot yeah so the smallest subunit and then these to fit on top of each other like so and in the proteins will be coming out at the end thing then the cytoplasm it's a jelly-like fluid mainly mostly made up of salt and water and this fills the cell and gives the cell it's shaped very important without the cytoplasm a cell would probably look like a deflated raisin and then it keeps the organelles in place then the nucleus which is the structure over here it stores the cells hereditary material in the form of DNA and then it also coordinates selectivities such as the protein synthesis which we'll look at in a later video and cell division there are more activities these are just some of the major ones then looking at the structure of the nucleus on this diagram on the right you've got the endoplasmic reticulum you've got the nucleolus let me get a different color the nucleolus over there and then you've got the nuclear membrane which is a double membrane surrounding the nucleus we've got the nucleoplasm on the inside the chromatin and in the nuclear pool so the nuclear membrane is porous to allow transport of material between the nucleus and the cytoplasm so that material can move in and out then the nucleoplasm is basically like the cytoplasm of the nucleus it has a jelly-like fluid or liquid that fills it on the inside then the nucleolus this round structure it produces RNA and ribosomes so this is where they are made and in the chromatin Network this pool of noodles noodle like structures that you can see inside the nucleus is a mass of genetic material that is composed of DNA and proteins that will form chromosomes if they clump together clump together as a bad word let's use the word condense so if they condense they'll form chromosomes next is the nucleic acids so there are two types of nucleic acids that you need to know of and that is DNA which I'm sure you've heard of before and dNA stands for deoxyribonucleic acid and then the second one is RNA ribonucleic acid now by the end we'll be able to make a table with the differences between the two but just reading the name the major difference comes in with the type of sugar so ribonucleic acid uses ribose sugar whereas DNA is deoxyribose sugar that is involved now nucleic acids control protein synthesis once again we'll look at that in a later video now the general structure of a nucleic acid it is made up of nucleotides so these three structures you see on the right all of them together makes up a nucleotide which is the building block of these nucleic acids so a nucleotide consists sry consists of a nitrogenous base a sugar that is a Pinto sugar bent meaning 5 so 5 carbon sugar 3 4 5 and in a phosphate group attached to the sugar so these three things make up a nitrogenous base and we'll look at that in more detail just a bit later on in the video especially with regards to the nitrogenous bases because there is a rule of thumb that needs to be followed their DNA structure and its functions so the exam guidelines a lot of the time will already give you information that you can study just straight from the exam guidelines and not even worry about looking at your textbook so in this case they've already given you the location of DNA where it is found so you can find DNA in the nucleus known as nuclear DNA and then another type of DNA that will become quite important when we look at the chapter of evolution and even genetics and inheritance is mitochondrial DNA find found in the mitochondria we will look at a brief history of the discovery of DNA with Watson Crick Franklin and Wilkins those four people are quite important and then we'll look at the components of a DNA nucleotide in more detail specifically the night jeana's basis that are involved there and then you need to know once again giving you the study material in the exam guidelines that the shape of a DNA molecule is a double helix you need to be able to use or draw a stick diagram of the DNA molecule to illustrate that structure and then lastly they've given you the functions of DNA already so basically DNA is therefore hereditary information to be carried on and then also the coded information for making proteins is found in DNA DNA is quite a long history but the discovery of DNA is attributed to these four scientists and it is also a bit of a controversial one there was lots of sneaky people moving around showing pictures that they shouldn't be showing to people that shouldn't be seeing it and let's start off with identifying these four people so this guy over here is James Watson then Francis Crick rosalind Franklin and then Maurice Wilkins so what something quick were already busy investigating DNA but so was rosalind Franklin and in 1951 she started at King's College College because she actually used x-ray techniques to study DNA structure she wanted to understand what DNA looked like and what its components were but so were Watson and Crick so in 1952 rosalind Franklin was able to take an x-ray photo of a chromosome so this was groundbreaking stuff this had never been done before and it actually took her there a hundred hours to get this image on the right hand side which is known as photo 51 and it's a very famous photo and this is a photo of a chromosome that she was able to take this was going to help determine the structure of DNA just by looking at that picture now by looking at that picture it just looks like a ax to me but do you then it was quite vital information but unbeknownst to rosalind Franklin Maurice Wilkins who she wasn't really getting along with took this picture and he went and he showed it to Watson and Crick and this helped them greatly with the research and looking at that picture they were able to come to a conclusion and formulate a basically a little model that the DNA structure is a double helix structure and that happened in 1953 so they released a paper just before rosalind Franklin it took her about a year to process all of the information she got from that photo and she also released a scientific paper on the structure of DNA and that came out just after days and that made it look like she was just confirming what they had found even though what she found helped them greatly she passed away in 1958 just before Watson Crick and Wilkins won the Nobel Prize for Physiology and medicine for the structure of DNA in 1962 so all of her hard work basically was never rewarded and for those of you that are interested this is what a Nobel Prize looks like just for interest sake and then I did put a link to a video on the discovery of DNA in the description tab below if you're interested in looking at that video because this is a very brief description of all the things that occur looking at the structure of DNA it is a double helix shape so the shape on the right hand side it's all coiled up and when it is uncoiled it will look like a ladder similar to this diagram on the right hand side now DNA molecule we've already discussed this is made up of nucleotides and the nucleotides are made up of a nitrogenous base a phosphate sorry a phosphate group and in a sugar group and these nitrogenous bases will differ so they are full nitrogenous bases associated with DNA it is adenine thymine guanine and cytosine now these nitrogenous bases can only bond with other nitrogen a certain nitrogenous base so in the case of adenine adenine can only bind with thymine and guanine can only bind with cytosine so cytosine will never bind with adenine or thymine and adenine will never bind with guanine or cytosine for example and the way I remember which ones go away is always together is for adenine and thymine they are always together and then gooning and cytosine make a good couple G for guanine C for cytosine good couple a for adenine T 4 thymine waste together so they will always bond with each other in that specific order now when you have to draw a stick diagram this is basically what you will have to draw so the nitrogenous base is attached to the sugar which is attached to the phosphate group then the phosphate group will attack attached to the next nucleotide which attaches to the sugar and nitrogenous base and then off of that sugar will be the next phosphate group so you can see how these nucleotides are basically building this DNA structure now that is only 1/2 the DNA molecule as the other half is on the right hand side and how these two legs of the ladder basically come together is through weak hydrogen bonds so the weak hydrogen bonds are found between the nitrogenous bases that's how they attach to each other and the reason that they have to be weak hydrogen bonds is because at some point yet the DNA is going to be unzipped so just like you unzip your jacket it's going to unzip and it's going to expose these nitrogenous bases so that they can be copied a bit later on during the process of DNA replication and protein synthesis so they will unzip and in there I exposed because there are these different nitrogenous bases the sequence in which they occur will give rise to certain proteins for example this could be going in and it can be adenine thymine cytosine going in these various combinations that can occur hundreds and thousands of them that will give rise to certain proteins so that is the general structure of DNA now we can look at the process of DNA replication so you need to know when in the sole it takes place so I'll cycle it takes place where in the cell it takes place how this process occurs without knowing the names of the enzyme so I won't even mention that in this explanation and then also the significance why is it important for DNA replication to take place so the process of DNA replication takes place in the nucleus during interphase of the cell cycle and in the process itself I have actually taken a a memo from a previous exam paper where they asked to explain the process of DNA replication as well as the important so that you can see precisely where marks are located so the process of DNA replication starts when the double-stranded DNA unwinds so from that foiled form it unwinds and it becomes that lattice structure then the next thing that will happen is that that lattice structure will unzip when those weak hydrogen bonds break and then each of those DNA strands acts as a template to form a complementary DNA strand and you can actually mention the nitrogenous bases but in the form of the base base so you need to mention that adenine will go with thymine and guanine with cytosine and then using the free DNA nucleotides from the nucleoplasm so those nucleotides that we looked at so that nitrogenous base attached to the Pinto sugar attached to the phosphate group there is free-floating nucleotides in the nucleoplasm so those are the ones that will be used to form these complementary strands and then to genetically identical DNA molecules are formed so let's look at this diagram on the right here so what will happen is this DNA molecule and whines and then it basically goes and lies in this ladder shape what will then happen is the weak hydrogen bonds between the nitrogenous bases started break and the DNA unzips much like it has yeah and when that happens these nitrogenous bases are now exposed and because they're exposed free-floating nucleotides so these groups of three in the nucleoplasm come in and they can try and find a partner for them so in the case of burning a night a nucleotide with a cytosine will come and attach to it their adenine will have a thymine this green is already bonded with a site scene and the thymine with the adenine inside carries on and on this side it will do the same so the cytosine that was actually with this guanine will now bond with a free-floating Groening this thymine that was with this adenine will bond with a free-floating adenine and in the end you have a complementary identical strand so they are two identical strands of DNA that are then formed and why does this have to happen this comes in with the importance so it ensures that each daughter cell gets an identical copy of the DNA after mitosis and then it also ensures that each daughter cell gets the correct number of chromosomes after mitosis which is very important DNA also comes handy in different situations in the case of DNA profiling or DNA fingerprinting DNA is also used so the definition of a DNA profile I also got from an old memo from a previous exam paper and it is the process by which the DNA of a person or an organism is mapped so its laid out oh the DNA sequence of an individual is determined or the ball code pattern of DNA is determined so looking at these diagrams on the right they look like barcodes and that is the DNA sequence that is then determined for each person where do we use the NA profiling so to investigate crimes to resolve disputes solve murders to identify organisms from there remain so if there's nothing else except maybe a few particles of bones of tissue you can use that to determine or identify the organisms to identify missing persons to identify family relationships other than paternity for example siblings or cousins to test for the presence of specific alleles or genes that cause a genetic disorder or to establish matching tissues for organ transplants that last one is quite important now now that we know their uses you also need to know how to interpret these DNA profiles and you will use it again in the chapter of genetics and inheritance when paternity testing is done you need to be able to to write about this in an essay even now this diagram at the bottom here is generally the one that you will see in an exam paper but let's look at this one at the top it's a bit easier to look at for now so this person was most likely murdered with this knife now on the knife you will find the DNA of the person that was murdered and perhaps the person that committed the crime also left some DNA maybe they cut themselves accidentally all these maybe some skin cells or something that was left on the knife that they were able to take and extract now because they are going to be two types of DNA on there we first need to kind of rule out the victims DNA on this murder weapon so that we can just compare it with the three suspects that they found so now we need to take out all of the corresponding barcodes of the victim on the the knife which means that that would be her DNA so let's cross our bet bar and this one and just I always have a ruler with me when I do this kind of thing just so I know I'm crossing out the correct barcode and just for interest sake just cross out the the ones that correspond with the suspect as well because it's not going to be that person so there's a match so this barcode is taken out of the account see these two if you this this is why use a ruler so you can see that these two are not lying across from each other so I won't cross those ones out these ones we can cross out okay so now we've cancelled all of the ball the ball codes of the ones that could be a match to the female so now let's see the remaining DNA should then be of one of the suspects now we need to see which of these suspects DNA matches the most with the whip and the DNA found on the weapon so here let's see who that corresponds with this one this one this one this one's a bit higher so it doesn't correspond the next one would be here corresponds over there and then lastly now we need to go see which of the suspects has the most corresponding barcodes with the DNA found on the weapon so suspect one has two corresponding barcodes suspect number two has three and suspect number three is completely innocent here's nothing so in this case the person that most likely committed the murder was suspect number two now this can also be used to identify paternity so same principle again you're going to go look which of the barcodes correspond with the child's so the mother and the child remember you get DNA from your mother and your father so let's just cancel out all of these okay now we can start and we can see which person was most likely the father so and this one though is to correspond that one and that one corresponds this one and this one corresponds so now we've looked at all of the DNA now let's see which one corresponds the most male 1 has 1 corresponding bar male 2 has 2 and male 3 has 3 so male 3 is the father of the child and that is the end of the first DNA video [Music] you