Mutant Detection - Video Tutorials & Practice Problems

Mutant Detection

in this video, we're going to begin our lesson on mutant detection or the methods that scientists can use to detect the presence of mutants. Now, scientists can identify or detect mutants by using two different methods of detection. The first method is the direct selection of mutants. And the second method is the indirect selection of mutants. Now in the method for direct selection of mutants, this method is only going to promote the growth of selectable mutants or mutants that can actually be directly selected for. However, this method will not promote the growth of the non mutant parents. And so only the mutants will grow and that makes it very easy for the scientists to select the mutant directly and easily. Since once again the mutant is the only thing that is going to grow Now. Unfortunately not all mutants can be selected for by direct selection. In fact, direct selection does not work for selecting Aqsa troughs. And so I recall that oxy troughs are going to be mutants that require additional growth factors. And the reason that directs election does not work on selecting oxy trough mutants is because PRO to troughs. The non mutant forms are always going to grow where Ozzy troughs grow. And so really there's no way to only allow for the growth of the oxy troughs without also allowing the growth of the PRO to trust. Uh And so if we take a look at our image down below. Over here, on the left hand side, which you'll notice is that this image is focusing on the direct selection of mutants. And what you'll notice is here we have a Petri plate, an auger plate. And this anger play is allowing for direct selection of a mutant. And so notice that this colony that you see here in red represents the growth of the mutant. And notice that there are no other colonies that are forming other than uh mutant colonies. And so what you can see here is if we zoom in that only the mutant, only the mutant will grow. And the other ones that are not mutants, noticed that they are dead and you can tell through their eyes are have these X symbols through them. And so because only the mutant is growing only promotes the growth of selectable mutants. It makes selecting the mutant directly. Uh it makes it possible to select the mutant directly and very very easily. Because once again all you gotta do is take that one colony and that is the mutant that you selected for. Now once again, direct selection of mutants is really convenient and straightforward and pretty easy. However, not all mutants can be can be selected for directly. And so those mutants uh like for example opposite ross which cannot be selected for directly, they must be selected for indirectly. And so this leads us to the second method of detecting mutants. And that is the indirect selection of mutants. And in this process both mutants as well as the non mutant parents are going to grow. And so what this means is that the mutants that are growing are also going to be growing amongst non mutants. And so the mutants have to be indirectly selected for amongst the crowd. And so if we take a look at our image down below, over here, on the right hand side, which will notice is that this image is focusing specifically on the indirect selection of mutants. And what you'll notice is that on this auger plate that both the mutant, which is going to be in red here as well as the non mutant parents are going to grow. And so it makes selecting for the mutant a little bit more challenging, a little bit more difficult. However, uh this is sometimes going to be a required process. And so what we can say is that if we zoom in that both the mutant as well as the non mutants are going to grow the non mutant parents. And so here, what we can say is that the mutants and the non mutant parents are both going to grow. And so again, this means that the mutant must be selected for out of the crowd. And so if you can imagine that these uh mutants are like Waldo from finding Waldo with direct selection, it makes finding Waldo or finding the mutant very, very easy and straightforward, since Waldo is the only one that grows, it's the mutant is the only one that grows however, within direct selection, then uh finding Waldo is going to be a lot more difficult. Finding the mutant will be a lot more difficult because again, the mutant will grow. But so will non mutants. And so in order to select for this mutant, it must be selected for indirectly using a specific method. And uh so what we're noticing here is that typically indirect selection is going to be a more tedious method, and it's only going to be used when it's required for identifying a non selectable mutant. Uh And so a non selectable mutant is a mutant that cannot be selected for directly. And so it must be selected for indirectly, for example, an ox a trough. And so the indirect identification of the mutant amongst the crowd can be accomplished via a method known as replica plating. And so we'll get to talk more about replica replica plating in our next lesson video. To talk more about how this mutant can be selected for amongst the crowd. But here, this here concludes our initial um introduction to mutant detection through direct selection and indirect selection. And once again, we'll talk more about replica plating uh in our next video. So, I'll see you all there

Which of the following is a major difference between direct and indirect selection of mutants?

• A. Direct selection finds selectable mutants while indirect selection finds non-selectable mutants.
• B. Direct selection is able to find auxotroph mutants while indirect selection cannot.
• C. Direct selection only allows the selected mutants to grow while indirect selection allows parent cells and mutants to grow.
• D. Direct selection is a more tedious form of mutant selection than indirect mutant selection.
• E. A and C.
• F. B and D.

A scientist has a population of His+ prototroph and His- auxotroph cells and wants to select and separate the auxotrophs from the prototrophs. Which form of selection should the scientist use?

• A. Indirect selection.
• B. Auxotroph selection.
• C. Direct selection.
• D. Any of the above forms of selection can be used.

Replica Plating

in this video, we're going to begin our lesson on replica plating. And so replica plating is a specific technique that's used to indirectly select for non selectable mutants which are mutants that cannot be directly selected for. And examples of non selectable mutants, our Aqsa troughs now, replica plating involves a series of three steps that we have numbered down below 12 and three. And the numbers that you see here in the text correspond with the numbers that you see down below and the image as well. And so that's important to keep in mind as we move forward. And so in the very first step of replica plating, what you need to do is play both the oxy trough mutants as well as the non mutant Pro to troughs. And you played these oxy troughs and pro troughs onto what's known as a master plate. And then you take the master plate and you press physically press the master plate onto a sterile velvet fabric. And then the velvet fabric will then contain the odds of troughs and proto troughs. And so if we take a look at our step number one down below and our image notice it's showing you the master plate over here in orange and the master plate contains both the oxy troughs which are in purple here, as well as the pro to troughs which are in blue here. And so then what you do is after growing both the oxy troughs and prototypes onto the master plate. You will physically press the master plate onto this sterile velvet that you see here, and so that leaves a colony imprint on the velvet, and so you can see now the colonies are here on this velvet as you see here. And so after the first step, you move onto the second step. And in the second step of replica plating, you then use that velvet fabric to inoculate too replicate agar plates. And these to replicate agar plates are going to be one will be a nutrient agar plate and the other will be a minimal media. And so the nutrient auger is going to contain additional growth factors that allow auxerre trough mutants to grow, whereas the minimal media is only going to contain the very bare minimum that's needed for the pro to troughs to grow. And so the Aqsa troughs will not be able to grow on the minimal media. And so if we take a look at our step number two down below right here, notice that you take a nutrient agar plate, and you physically press it down onto the velvet to transfer the colonies over to the nutrient agar plate. And then you do the same with the minimal media plate. You press this down onto the velvet and again transfer the colonies onto the minimal media. And so at this point this takes us to step number three, where the plates will be incubated and then observed. And so what you'll find is that the Pro to troves which are non mutants. Uh they will be able to grow on both the nutrient agar plate as well as the minimal media plate. However the odds a trough mutants will only be able to grow on the nutrients auger plate and the dogs. A trough will not be able to grow on the minimal media. And so if we take a look at our image down below, which will notice is that the nutrient agar plate is going to contain both Pro to troops as well as the opposite rose. And so both of these will grow as you see here on the nutrient auger. However on the minimal media which is lacking those additional growth factors needed for the oxy troughs. Only the pro to trump's grow. And so the odds are troughs do not grow. And so by the missing positions these little dotted circles that you see here represent the missing oxy troughs. And by the positions of these missing auxerre troughs, you can trace them back to these positions that you see in the nutrient auger. And then you know that these colonies here growing on the nutrient auger must be the mutant opposite ross. And so at this point you could then select these mutant oxy troughs and these mutant oxy trophies have been indirectly selected for by replica plating, creating these to replicate plates. And so this year concludes our brief lesson on replica plating and how it can be used as a technique to indirectly select for non selectable mutants such as oxy troops. And we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.

Replica plating is an example of which type of mutant selection?

• A. Auxotroph selection.
• B. Direct selection.
• C. Indirect selection.
• D. Secondary selection.

What types of bacteria will be growing on the nutrient agar and minimal media at the end of a replica plating experiment?

• A. The nutrient agar will possess prototroph bacteria, while the minimal media will possess auxotroph bacteria.
• B. The nutrient agar will possess both prototroph & auxotroph bacteria, while the minimal media will possess prototroph bacteria.
• C. The nutrient agar will possess auxotroph bacteria, while the minimal media will possess the prototroph bacteria.
• D. The nutrient agar will possess auxotroph bacteria, while the minimal media will possess both prototroph & auxotroph bacteria.

Why do prototroph bacteria grow on minimal media but auxotroph bacteria do not?

• A. The minimal media does not possess the growth factor the auxotrophs need to grow.
• B. The minimal media does not possess growth factors, but prototrophs do not require growth factors to grow.
• C. The prototrophs outcompete the auxotrophs for the minimal nutrients found in minimal media.
• D. Prototrophs and auxotrophs are not able to grow together on the same plate.
• E. A and B.
• F. C and D.

Which of the following colonies of bacteria are composed of His- auxotroph bacteria?

• A. A, C, D, F, & H.
• B. B, E, & G.
• C. A, B, E, & F.
• D. All of the colonies are composed of His- auxotroph bacteria.

What characteristics are true about the colonies living on the minimal media plate?

• A. These colonies do not require histidine to grow.
• B. These colonies are composed of His+ prototroph bacteria.
• C. These colonies do not require growth factors to grow.
• D. There are not His- auxotroph bacteria present in these colonies.
• E. All of the above statements about the colonies living on the minimal media are true.