VCE Biology Question Thread

[sweetcheeks]

Q17 2013 --> What good would isolation do? The kangaroos and wallabies are infected and mosquitoes carry the virus to humans. You can't simply isolate the mosquitoes, they are able to move out of the isolated areas and infect.

Q40 2013 --> You want to reduce the use of antibiotics. D implies that after the bacteria is made more permeable to antibiotics that antibiotics will be given to kill them. You want a method without requiring antibiotics.

[vox nihili]

I tend to mix both together (not sure if it's right? but I've been getting full marks for immunity questions that describe the action of a vaccine)
- T helper cells release cytokines to stimulate the clonal expansion of clonal selected naive B cells which detect specific antigens as non-self, which divides and differentiates to form antibody-producing B plasma cells, and B memory cells......(continue)

This is pretty well the case. B-cells won’t undergo clonal expansion without having bound to the antigen against which it is specific.
The T-helper cell’s role in this is to basically make the clonal expansion more significant, sort of acting as a cheerleader pushing it forward.

[ezferns]

Ah ok, silly mistake by me

Are T helper cells necessary in clonal expansion or can B cells proliferate and differentiate without stimulation from T helper cells?

[vox nihili]

Ah ok, silly mistake by me

Are T helper cells necessary in clonal expansion or can B cells proliferate and differentiate without stimulation from T helper cells?

I’d really encourage other people’s input on this, because I’m not entirely sure where VCE draws the line.


The answer is yes and no. B-cells will proliferate, but only to a point. They won’t differentiate. It’s really quite a limited response, such that it’s practically meaningless.
So T-helper cells are essentially required to effect clonal expansion, yes.

[LifeisaConstantStruggle]

Ah ok, silly mistake by me

Are T helper cells necessary in clonal expansion or can B cells proliferate and differentiate without stimulation from T helper cells?

I have edrolo and Douchy (ma man Douchy the bio teacher) mentioned that selected B cells generally require a signal from T helper cells to undergo large-scale clonal expansion, this might be a simplified explanation for us VCE plebs but an explanation nonetheless.

[Sine]

Ah ok, silly mistake by me

Are T helper cells necessary in clonal expansion or can B cells proliferate and differentiate without stimulation from T helper cells?

in terms of vce proliferation and differentiation go hand in hand and yes for vce you definitely need T helper cells to activate the specific B cell

[vox nihili]

It’s never been very clear in previous study designs unfortunately, with the role of T-helper cells sort of ascribed to this weird and vague role in “beefing up” the immune system.
I largely agree that they seem to have clarified this and will expect that knowledge now.

[ezferns]

So I reckon I should just mention T helpers if a question comes up on that?

Another question: if I'm testing the effect of temperature on the action of an enzyme, would the dependent variable be the rate of reaction of the enzyme or the rate of production of products?

[PhoenixxFire]

I have just being saying that t helper cells cause them to divide and differentiate further for Tc cells and that it causes them to divide and differentiate for B cells (difference due to the way I structure my answers-I posted them in response to a question somewhere in a different bio thread if you want to read them) and I've been getting full marks from my teacher.

I'd say it depends on what you are measuring, if you're measuring the amount of product produced saying that would be more accurate.

[Bri MT]

So I reckon I should just mention T helpers if a question comes up on that?

Another question: if I'm testing the effect of temperature on the action of an enzyme, would the dependent variable be the rate of reaction of the enzyme or the rate of production of products?

the dependent variable DEPENDS on the other one. Rate of reaction depends on what the temperature is (plus other factors obviously) and is the DV.
(the DV is also shown on the y-axis of graphs, so thinking of what the graph looks like might help you answer this)

[ezferns]

Oh ok so the dv is the thing that is directly affected

Sorry for asking so many questions but how are ppl heterozygous for sickle cell anemia selected for in malaria persistent countries? Wouldn't they have the same phenotype as those homozygous for the normal allele?

[PhoenixxFire]

No they would not have the same phenotype. Sickle cell anemia is co dominant so both the healthy and SCA alleles are expressed (like AB blood type). This gives the person a milder form of sickle cell anemia which they can live with, however it also makes it harder for malaria to infect them, which gives them a selective advantage in countries where malaria is common.

[simrat99]

What is the difference between translocation and insertion mutations?

[PhoenixxFire]

Insertion is a copy being inserted into a different DNA segment - the original is still in the correct place as well. A translocation is the original moving to a different DNA segment - there is only the one copy though.

[simrat99]

Insertion is a copy being inserted into a different DNA segment - the original is still in the correct place as well. A translocation is the original moving to a different DNA segment - there is only the one copy though.

Thank you!