hi there and welcome back to national 5 biology you know one cell biology in this lesson we will be working here 3 which is DNA and the production of proteins so looking back in the first couple of key areas we have previously cell biology what you should hopefully remember from cell biology is that a cell contains a nucleus and the nucleus contains genetic information that's what we agree focusing on for the rest of this lesson so in this first example here we want to look at the difference in size in genetic information so in the cell there is a nucleus when you look very very close enter nucleus you will find chromosomes which we'll look at in more detail later on chromosomes are fuel against them they are made up of genes and the genes are strands of DNA DNA is something you may have come across before and TV shows or movies but we're going to look at what DNA actually does so the point of this slide is to show you the difference in size first thing nucleus being the biggest chromosomes smaller gene smaller and DNA being the smallest part of genetic information this site goes on to that more detail this is something that is often used in classes just to show you the different structures so if we look at a cell we have to clears again like I said once you look at the nucleus you look at chromosome however the chromosome is made up of chromatids which are held together by a centromere in the middle once that unravels when we start looking at the genes so your strands of DNA this strange twisted ladder shape is made up of a backbone and then basis butter in the middle so if you imagine the sides of the ladder as a backbone and the middle rungs are bases and the bases are the next thing that we are going to be looking at so with DNA this twisted ladder ellipta has a certain name as double stranded helix and this structure is held together by these bases these complementary bases that were going to look at and the next couple of slides the important thing to know as well this is the point of DNA the point of the genetic is used to make proteins I'm not going to look at what these proteins are and the next couple of lessons as well so going back to DNA DNA is composed of four different bases I need to know all of them C G a and T but more specifically cytosine guanine adenine and thymine good ones look at how these work together and how this makes up the structure of DNA so each of these bases pair with a complementary base which means the one name match with they don't match any are cytosine pairs of guanine and adenine pairs with thymine so cytosine for example cannot appear with adenine or if I mean it can only appear with quani you need to know these off by heart very very common exam question the way I like to remember this is that CMG are both curved letters so if you think the two curve planters match together and E and T or at match together as well to look in a bit more detail structured DNA if remember back this double helix structure is a the backbone of DNA is made up of a phosphate and a sugar let's say attach the base the base there time she is to a complementary base pair and then there'll be another sugar and our phosphate this structure here of the phosphate the sugar in the base is called a nucleotide you don't need to know any more detail a national 5 level this slide shows a lot more detail so for example you have the blue circles the phosphate the red sugar and then the base of E or adenine named thymine day in the sugar database phosphate when we look at DNA girls could be looking at something called mRNA ok our messenger RNA which is a different form what you really need to do with this level it's not a Marilee a single-stranded so only one strand whereas DNA is double-stranded like o suta for the double helix what we're looking at as I said previously is that Jack information founded DNA makes proteins however DNA needs to get from the nucleus so where genetic information is bound to the ribosomes which hopefully you remember is the site of protein synthesis or the making of proteins the only problem with this is that DME is quite large with those double helix shape in terms of cell biology mRNA have the smaller and that is used to care of nucleus so the genetic information from DNA who needs to move from the nucleus to the ribosomes in order to make proteins now we're going to look at the stages of these in stage one the DNA double stranded helix DNA starts to unwind so good supper being unzipped and two separate strands what then happens is the complementary mRNA molecule is made and lanes up with these single strands now so for example if one of the strands was e T G and C then T a CG would be the complementary strand I mean my mRNA so these species pick up according to the SP SP rules of eclipta in stage 3 the new mrna strand leaves the nucleus it's a part stop if the compound should be appearing from the DNA the mRNA moves through the nuclear pores towards the ribosome what then happens at the ribosome is the mRNA strand is read with this genetic code and the order of the bases is used to make amino acids these amino acids then join together in order to make protein so DNA to mRNA then grows the ribosome today make amino acids and they join up to make a protein this time I'm here is probably a worth looking down and then maybe going back through the last few slides I write down the steps 3 1 2 3 & 4 because that shows the whole process you have double stranded DNA double helix unzips on wanes the mRNA comprehension molecules come across name of a nucleus to the ribosome with mRNAs and red and two amino acids and then meat and two proteins that is only in its no Pulaski area it's a as a common carrier for questions you through all the steps looked at and really one of the main things you need to know just off the top your head every single time are the base pairing rules of ACGT couple of paths paper questions in this one before I get to the quizzes questions so this is one for a few years school ask you to name molecule why so liquid on beforehand I'd like you to pause this go through it later on and I'll talk you through the answer so hopefully you've lit first of all this is inside the nucleus so it has to be the DNA there's a double helix it has been unzipped it means the molecule Y must be the mRNA that's came and it's going to be a complimentary reading of the a G a G a a today I go across at the ribosome so the extension to this question could be what are the complementary bases all this one's asking is what is molecule Y which is mRNA in this question it's asking you the basic units which are joined together to make a protein at the ribosome so you should hopefully remember that the mRNA comes the ribosome the jerk with is read and there's the internal two amino acids amino acids are joined together to make a protein at the ribosome this is a very common question and a reason why you have to know all of these complementary bases you could be getting a DNA strand and you have to get two complementary DNA strands at the Orient so for example in this long line here of 80 g cg 8 t GC g c TG TC your complement a swede b ta c GC ta CG CG a CAG just remember that a match is with T and C matches of G and you always get the mark for these questions this question here again protein samples us ask you DNA contains Tekken Geoffrey material which controls the senses of a chemical made from amino acids name the type of chemical synthesized again just try and get into your head at the ribosome site of putting some process amino acids are synthesized or made into proteins and the diagram above but should not seen shows a section of the code to make a protein such as families the strafe headers could to make the protein insulin would differ from this so you don't need to know if layoffs in this question all is asking is here with these codes be different hair the code for Emily's be different from the code for and so on and all we need to know as a different sets of information are different orders of base pairs code for different proteins that is why do you be different they have a definite order of base pairs therefore amino acids name different proteins so this is quite a short key area but its water advised to go for quite a lot mate renew is all off my heart you'll get all the questions totally right and the exam again I'll Leia set up the quizzes fight so much for following these I'll get the next key area okay soon and all some people have been commenting about exams coming up so we'll try and get through the rest is bias Marshall following readable information and answer questions thank you