in this video, we're going to begin our lesson on proto troughs versus Aqsa troughs. And so first we need to understand that some cell mutations can actually alter their growth factor requirements or what growth factors need to be present in order for them to grow and survive. And so these mutations that alter the growth factor requirements of cells leads us to these two groups, the PRO to tropes and the Aqsa troves. Now the pro to troves are commonly represented with a plus sign as you see here. And so the proto troves represent the original parent strains that have no mutations and therefore because they have no mutations, they do not require any additional growth factors. And so the root proto, which is found in the word proto trophy, is a route that means the original form. And so once again, these proto tropes are the original parent strains. They have no mutations and therefore they do not require additional growth factors. Now, the reason that they do not require additional growth factors is because these pro to troops have functional genes that allows them to synthesize or build or make their own growth factors from other molecules. And so those growth factors do not need to be in the immediate environment. Those growth factors are not really required to be present in the immediate environment. And this is because these prototypes have the ability to use completely different molecules to build to synthesize the growth factors that they need to survive. Now the opposite troughs, on the other hand, are commonly represented with a minus sign as you see here, and these oxy troughs. Unlike the pro to troughs, these are mutants that are going to contain mutations in the DNA. And these odds intros contain specific mutations that require the odds are troves to have additional growth factors. And so um the root Akzo which is found in the word Oxo trough is a route that means increase and this is referring to the increased additional growth factors that are required. Now. The reason that these oxy troves require additional growth factors is because once again these oxy troughs are mutants that have mutations in the DNA. And these specific mutations that the oxy tropes have actually prevent these are exit trophies from synthesizing their own growth factors from other molecules. And so the oxy troughs are not able to create the growth factors that they need. And so those growth factors that they need, they must be provided and available in the environment in order for them to grow and survive. And if they're not available, if those growth factors are not available to opposite troves then they will not be able to survive. And so once again the oxy troughs are mutants that require additional growth factors. Now here's a little memory tool to help you remember that the plus sign once again represents proto troughs. And so you can use the peas here to help you remember that proto troughs are represented with the plus sign and of course the minus sign as you see here is going to represent the opposite ross. And so in our example down below, we're going to look at History Dean, Pro to troughs or His plus cells. Since again the plus represents Pro to troops. And we're also going to look at histamine oxo troughs or hiss minus cells where again the minus sign represents the oxy troves. And so history dean is one of the 20 Amino acids that are used to build proteins. And so histamine is required for cells to build their proteins. And so History in in this case is going to be the growth factor of interest. Now Pro to truce. Like what we see over here on the left are again going to be the original parents trained with no mutation. And they do not require these additional growth factors. And so the notice that the pro to trope is represented as a hiss plus bacteria because the plus represents the Pro to tropes. And His plus just means that it has a normal His plus jean that does not have any mutations. And this normal His plus gene that does not have any mutations allows the PRO to trophy to synthesize its own growth factor. And so the pro to trove can synthesize its own histamine using other molecules. And so as long as the pro trump has this normal his plus gene. It can make its own histamine and that histamine does not have to be available in the environment. And so notice that these proto tropes have the ability to grow either with or without history because it can make its own histamine as long as it has this normal hiss plus jean. And what you can see here is that the pro trump is capable of dividing replicating. And uh it can replicate of course to create another pro to trope. But if a mutation occurs and one of the cells then it can generate what we call an og zoetrope. And the odds a trove. Once again it's gonna have increased growth factor requirements. In this case the oxy Trophy is going to require his stunning to grow. And the reason for that is because the exit trough is a mutant. And so it is a mutant. His minus bacteria where again the minus sign represents the OG Citro. And so this mutant his minus bacteria has a mutation in the gene. And so we call this a mutant his minus gene and the mutant his minus gene. Because it has that mutation it prevents the synthesis of its own growth factor. And so it prevents the synthesis of its own history. E and so what that means is that histamine must be available in the environment in order for the dogs A trove to grow. And if histamine is not available in the environment for the exit row then the odds A Trophy is going to die. And so this cell requires Historian to grow. Whereas the Pro to trophy does not require historian to grow because it is capable of synthesizing its own history in from other molecules. And so once again it's important to keep in mind that proto troughs are represented with a plus symbol and oxo troughs are represented with a minus symbol. And so this here concludes our brief introduction to Pro to tropes and Ozzy tropes and we'll be able to cover an example problem and more practice applying these concepts as we move forward in our course. So I'll see you all in our next video.