0:00 so we're talking about viruses today and we're going to look at some types of viruses so here's HIV uh you've got your RNA inside and your protein coat um which is a caps on the capsid and then you've got um a lipid layer on the outside here's Ebola to actually a really big virus here's a herpes virus and this is what it ends up looking like um when it erupts in your face and here's an adenovirus which is a common cold influenza virus remember there are lots and lots of different types of um flu viruses lots and lots of different types of cold viruses um papiloma virus causes warts and then here's a bacteria FES
0:48 which is really important because we're going to be talking about it um when we do a a unit on DNA and so this one is kind of an important one so here's the DNA um and this whole thing is a protein coat and it infects bacteria as its name suggests so here's a bacterium and here's um some viruses and you can see the the DNA is colored here um in this case green I guess and it's it's like a hypodermic needle this thing squishes down and it injects um the DNA inside and so you can see the pins here and that's what um helps to get the DNA inside the um the bacterial cell so here's a video of it which isn't going to work for you but anyway these are viruses that attack bacteria and so
1:35 you can see them attaching to the bacteria here and injecting the DNA inside so a virus that attacks bacteria is called a bacteria Fage or Fage or if you want to just call it a phage that's fine a lot of people say F so there it is there's an um picture of it with an electron micrograph which is a kind of an amazing shot I think t FES are a specific class of bacteria phases that look like this and so again it's got its DNA and then it's got the protein around it you don't have to memorize any of the parts of it um just remember that it looks like a needle I think it does anyway and here's what ecoli looks like so T4 phases infect ecoli which is a type of um bacterium and it's found in
2:22 the intestines so it's an intestinal bacterium so everyone has ecoli in them there are some strains of eoli that are pathogenic that can hurt you um so that's one reason to boil water if you're not sure whether it's clean or not if you find ecoli in your drinking water let's say um the government comes and tests you're drinking water and they find ecoli in it that means it's an indicator organism that means that it's very likely that that water was contaminated with poop from either people or cows or something so there are six small spikes um at the base of this contractile sheath that are used to attach to the host cell these things are kind of sinister looking because they are um and then they inject the viral DNA into the
3:10 cell and then there are um two different types of bacterial phage replication there's the litic cycle and the lysogenic cycle and so the well let's go backwards for a second um either the the virus can go into either one of these cycles and if it goes into this one then it can come out later and go into this one so let's look at each of them first we'll look at the litic cycle um Lis means to burst so the first thing they do is attach to the cell and there the virus is attached to the cell here is this is a bacterium and so it has one chromosome that's circular and here's the DNA that's in the virus so you can label that the bacterium and that's the bacterial
3:56 chromosome which means it's one DNA strand and that's the virus so the next thing that happens is it injects the viral DNA or RNA um in this case it's DNA so there it goes and I don't know if this is going to come out on the screen capture but it's showing the DNA um going right into the host cell so then the next thing that happens is that replication happens so replication of new viral proteins and nucleic acids so this can only happen in the host cell because you actually need um all the nucleic acids and the proteins the amino acids um you need some enzymes that are only found in the bacteria not in the virus so here the remember how we said viruses don't grow
4:42 they assemble so the viral DNA is telling the bacterial cell it's directing the bacterial cell to make a whole bunch more viruses so more viral DNA enclosed with um this protein and then the other pieces will get assembled on and then um so you have the Assembly of the new viruses so you have this part that attaches to that part it's kind of like putting Legos together this goes with this blah blah blah blah blah and here you have the assembled new um virus and so you're going to make lots and lots of viruses um when one virus infects a cell you're going to make many many many many many um new viruses and then bummer here we go the release of the new viruses into the environment so they break open or lice
5:27 the bacterial cell when um viral replication is finished so this litic cycle ends in cell death for the bacterium and so I'm not sure if this video will work but you're injecting the DNA in here then the DNA um replicates and it it uses the host enzymes and stuff or maybe one of its own enzymes to replicate and then to make all the proteins that it needs and then they all get assembled and then they um are released from the cell when the cell explodes what a bummer huh lysogenic cycle is a quieter one at least for a while so some viruses have the ability to become dormant inside the cell that's called the the latent viruses so not all viruses do that but
6:14 the ones that do can kind of um go into the cell and just lie quiet for a while so they remain inactive or dormant means the same thing dormant means inactive for long periods of time later they activate to produce new viruses in response to some signal so here's the DNA going in and instead of replicating it's actually going to insert itself inside um the viral chromosome so viral DNA is injected into the host cell the viral DNA joins the host DNA forming um a prophase
7:00 and so let's take a look at that so here you have let's see um here you have the virus that came in this part is now the viral DNA that's been injected but now it's part of the bacterial chromosome so this green part is bacterial chromosome and of course chromosome means DNA propage that's this part here and that means means the virus DNA and so what happens is it just lays low it doesn't do much and so when the cell division occurs now you have two new um cells that both have the virus so you can end up having lots and lots of viruses replicated just because the
7:46 bacterial cell is replicating so the viral DNA may stay inactive in the host cell for long periods of time the propage is replicated during each binary fish so we haven't talked about binary fishing yet but that means replication that's what's happening right here it's replication in a bacterial cell or a procaryote over time many cells form containing the prop phases and so hopefully this video will come out here you have this will be hopefully better than the last one so here you have the viral DNA and it's going to get injected into the host cell so when an activation okay hopefully this thing will play it has to have the right
8:33 receptors and then it's going to inject its DNA and there it goes injecting its DNA and then that DNA is going to actually um go right into the the host chromosome so here it is it inserts itself in and now you have the proage and the whole entire chromosome so when an activation signal occurs the phage DNA start starts to replicate so that did you see that just come out um that's what would happen so once a propage cell is activated the host cell enters the litic cycle and we're back to that other one where the cell just makes a ton of viruses and the cell dies bummer so new
9:19 viruses form and the cell lices and bursts okay so here's the picture of the whole thing so we've got let's see right here number one that's when the virus is injecting its DNA and so it might go into the litic cycle that's this one right here and so here's the bacterial chromosome and here's the viral chromosome the viral chromosome says okay I'll make a bunch more of me and so it does it makes a bunch more viruses like itself and then it breaks the cell and all the viruses go off to infect something else or instead of that when the viral DNA gets injected inside it actually can sometimes become part of the bacterial chromosome as a pro F or propas and then the bacterial cell can reproduce um it's called binary fishion
10:06 and so it reproduces and you can see this many cell divisions it can actually divide and divide and divide you can have a ton of V of bacterial cells like this that all have that virus in them anyway at some point by some signal um the viral DNA can come out here it is and it can go right into the litic cycle when a virus infects the cell and starts producing more viruses right away what cycle is it and that's the litic cycle when virus when a virus infects a cell and inserts its DNA into the host DNA what is that Viral DNA called that Viral DNA super phage proage lag phage latent phage it's called a propas or profile which cycle is represented here
10:53 so you have the DNA going inside the chromosome of the bacterium so that's the lysogenic one so it's B lysogenic okay latency and viruses that attack UK carots um I think we'll pause here
