AAMC fl2 bb 40-41

[Hurricane 20]

I have problem with their graphs and their answers are confusing. Could someone help break it down please? Thanks in advance

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[funtimes543]

It took me a while to figure out this graph but here's what I came up with.

So first of all, the proteases which are the gene products of CatB and CatL are needed for infection.

In the graph:
the top section, "culture cell genotype" shows you how they altered the cells.
So if it is WT, it's CatB++ and CatL++ meaning it naturally is able to produce both CatB and CatL (so it should be able to infect).
Next is the CatB-- and CatL++. This would be able to naturally make the protein for CatL but it would not be able to make the protein for CatB.
And the last one, CatB-- and CatL-- would not be able to naturally make either protein.

So now, we can look at the bottom section "introduced genes." I thought of this as what they added to the cells.
In our CatB-- and CatL++ they tried adding CatB and adding CatL separately. Remember that this cell is able to make the protein for CatL on its own because of its genotype.
Looking at introducing the CatB gene in CatB-- and CatL++ we can try to figure out whats in the cell now. So its going to have the CatL protein because it can naturally make it and its going to have CatB because we added it (by introducing the gene). So this cell is going to have both CatL and CatB proteins and we can see that it has the highest percent for infection based on the y axis.

Next is introducing the CatL gene in CatB-- and CatL++. So the cell is still able to make the CatL protein on its own and we even added some more letting us know that it has a bunch. But there is no way for the cell to make the CatB protein. And we can see that this has very low infection, letting us know that when the cell has only CatL, it can't infect. At this point we are sure that CatB is required for infection. But we aren't sure if CatL is actually needed.

So now we can look at the CatB-- and CatL-- genotype. This means the cell is not able to naturally make either one of the proteins on its own.
When CatB is introduced on its own, there is a tiny bit of infection going on.
When CatL is introduced on its own, there is almost no infection
But when CatB + CatL are introduced together, we can see that this cell has significant infection. This follows the results of the CatB-- and CatL++ experiment. So now we know that in order for optimal infection to occur, the cell must be able to have both CatB and CatL, either by making it on its own via the genotype or by it being introduced.

That directly gives us the answer for 41. For 40, you have to go through the choices carefully to see if what they claim is true is actually true. For choices A and B, the reasoning they provide is correct (VSV-EGP DOES infect cells expressing CatL better than it infects cells not expressing CatL AND VSV-EGP DOES infect cells expressing CatB better than it infects cells not expressing CatB). But the question asks if CatL expression is sufficient, and we know that it isn't so the answer must be C or D. Choice D also provides correct reasoning (VSV-EGP DOES infect cells expressing both CatB and CatL better than a cell expressing only CatB) but that doesn't follow the reasoning of the question. The question specifically asks if CatL expression is sufficient.

I know this is a lot but really the only way I can understand stuff like this is by breaking it down to the most simple form. So hopefully, that helped someone.

 

[Rihannalover]

Thank you and God bless you! I couldn't wrap my head around this graph

 

[treeclimbingmonkey]

Thank you, but do you know what the "bacterial" introduction gene is? This kind of confused me as well.