VCE Biology Question Thread

[Biology24123]

When T helper cells proliferate, effector and memory cells are produced. These effector cells then activate cytotoxic T cells which also produce memory cells. Does this mean during the 2nd exposure, both types of T memory cells are required?

Also, after APC's recognises a pathogen, it travels to the lymph nodes to interact with T helper cells. So once plasma cells are produced, how do they travel to the infection site

[cosine]

When T helper cells proliferate, effector and memory cells are produced. These effector cells then activate cytotoxic T cells which also produce memory cells. Does this mean during the 2nd exposure, both types of T memory cells are required?

Definitely, yes. Say the pathogen recurs the second time, the memory T Helper cells will be in abundance, and so macrophages are easily able to locate one of these to activate it to proliferate, once activated, the T helper cells, in abundance, locate also the cytotoxic T cells, which are also in abundance from the first exposure. Once activated the Tc cells, then the rest is the same as first exposure. But, as Mr T Rav said, this is probably too much and VCE biol only talks about memory B cells, so I will keep that in mind when answering immunity questions regarding third line of defence.

Plasma cells don't necessarily travel to the infection site, they produce and secrete antibodies that travel via the blood stream or plasma to the infection site. B cells are generally found the in lymph nodes and spleen, probably not in abundance anywhere else.

Second this.

Non-disjunction means that the homologues haven't separated, so no, this won't be the case. Meiosis I and meiosis II would occur as normal if you start off with one less chromosome, you'd just end up with two daughter cells without that chromosome and two with a full set.

Although, the reality of the matter is that if someone were missing one chromosome, they wouldn't be able to grow to a point whereat meiosis would even be relevant. In other words, lose a chromosome, and you'll probably die. So, theoretically, yes, both stages of meiosis could occur. Practically, however, the organism would be so buggered meiosis wouldn't occur.

Thanks, so you're saying that meiosis can still occur even if homologous chromosomes are missing, but for example if two different species mate, they can produce offpsring, but the offspring will not be able to reproduce. If so, why can't the offspring not be able to reproduce? This was on my prac exam and I just said because the F1 offspring cant reproduce fertile and viable offspring because it would not have homologous chromosomes?

What I am trying to find out is, when does meiosis actually not occur?

[cosine]

Why on earth is the answer not A? Leucocytes are white blood cells, hence lymphocytes are a branch of leucocytes?

[cosine]

Thank you so much:)

Can you answer my theory of gel electrophoresis please? What do you mean by the size of fragments and not their identity, because if two lanes has different sized fragments, then does that not imply that they were two different people because if it was the same person, it would obviously have the same sized fragments? o.o

Also for question 10 b (attached) the answer says that the woman would not be able to reproduce because her X chromosome would not be able to pair up with another sex chromosome. I dont really understand this, because can't meiosis occur even though there is a missing chromosome? I thought that because there is that one missing sex chromosome, then the baby has a higher chance of receiving a less chromosome (monosomy).

Mr T-Rav, this is an example of my question I posted a while back (no one answered )
Any help, please?

[Biology24123]

Definitely, yes. Say the pathogen recurs the second time, the memory T Helper cells will be in abundance, and so macrophages are easily able to locate one of these to activate it to proliferate, once activated, the T helper cells, in abundance, locate also the cytotoxic T cells, which are also in abundance from the first exposure. Once activated the Tc cells, then the rest is the same as first exposure. But, as Mr T Rav said, this is probably too much and VCE biol only talks about memory B cells, so I will keep that in mind when answering immunity questions regarding third line of defence.

Plasma cells don't necessarily travel to the infection site, they produce and secrete antibodies that travel via the blood stream or plasma to the infection site. B cells are generally found the in lymph nodes and spleen, probably not in abundance anywhere else.

Thanks

[Biology24123]

Why on earth is the answer not A? Leucocytes are white blood cells, hence lymphocytes are a branch of leucocytes?

I'd say it's B. Leucocytes aren't specific to cellular immunity. The Thymus is where T cells mature

[cosine]

I'd say it's B. Leucocytes aren't specific to cellular immunity. The Thymus is where T cells mature

But T cells are leucocytes thats why I chose A ?

[Biology24123]

But T cells are leucocytes thats why I chose A ?

A is a very general answer, maybe it's right but B is the most correct answer I'd say

[cosine]

Is this question worded properly?

"The macrophage T-Helper cell complex stimulates other cells and chemicals to target and damage..."

Does the complex activate the B cells to proliferate, or does the Helper T cell get activated upon this macrophage complex and travels to the B cells to activate them?

[KingDrogba]

In relation to Stem Cell Therapy could someone help me out with these questions:

How does the technique manipulate the genetic material?   
Can the genetic changes be passed on to future generations?

Much appreciated

[BakedDwarf]

Why on earth is the answer not A? Leucocytes are white blood cells, hence lymphocytes are a branch of leucocytes?

Natural killer cells are lymphocytes that destroy virus-infected cells.

[cosine]

Natural killer cells are leucocytes that destroy virus-infected cells.

Natural Killer cells are not in the study design

[vox nihili]

In relation to Stem Cell Therapy could someone help me out with these questions:

How does the technique manipulate the genetic material?   
Can the genetic changes be passed on to future generations?

Much appreciated

You're introducing new cells with, potentially, different genetic material. Therefore, that's how it changes it.
Couldn't be passed on because stem cell therapies replace somatic cells. To be passed on you'd need to use stem cells to replace gonadal (i.e. testicles/ovaries) cells.

Natural Killer cells are not in the study design

Not sure this is the case. Could be that the study design has changed since that question. Don't forget the revision in 2013 to the study design.

Mr T-Rav, this is an example of my question I posted a while back (no one answered )
Any help, please?

Not really sure about your fragment question. In the question we were talking about, we had no idea where the samples came from, so we can't make any conclusions at all about their source or the identity of the fragments involved. Just because two fragments in different lanes are of the same size does not mean that they are the same fragment. That something is, for instance, 400 bp long does not serve as an identifier of that fragment. There are, quite literally, 6.668 x 10²⁴⁰ different DNA fragments of 400 bp possible.

[cosine]

For attached questions:

1. This is exactly what I wrote the paper, would I get the 3/3 marks or not, if not, please tell me what I need to change? Cheers

The poison Ivy toxin would have entered Paul's interior and must have been engulfed by macrophages, these macrophages will degrade and present fragments on their MHC Class II markers to activate specific Helper T cells. The Helper T cells will then activate specific B cells that also possess the toxin on their MHC II markers and are activated to proliferate into plasma and memory B cells. The plasma B cells will secrete specific IgE antibodies that will bind to mast cell membranes, when the toxin binds to these IgE antibodies, they stimulate the mast cells to degranulate and release histamine, which causes vasodilation of the blood vessels and increases permeability of capillary walls to increase the blood flow to the site of infection.

2.

For the second attachment, I did not talk about the speed of the propagation of the action potential at all.. I only said that in the given info, the hormone travels along the axon, whereas in the typical transport, the action potential travels along the axon. I also said that in the give example, the hormone is released to the blood vessels whereas in the typical neurone, the neurotransmitters are released in the synaptic gap to diffuse through to the post synaptic membrane.

What do you think? Would this get marks on the exam, because the assessors report only spoke about relative speeds of the thing, but the question specifically said 'transport'?

Many thanks in advance

[cosine]

You're introducing new cells with, potentially, different genetic material. Therefore, that's how it changes it.
Couldn't be passed on because stem cell therapies replace somatic cells. To be passed on you'd need to use stem cells to replace gonadal (i.e. testicles/ovaries) cells.

Not sure this is the case. Could be that the study design has changed since that question. Don't forget the revision in 2013 to the study design.

Not really sure about your fragment question. In the question we were talking about, we had no idea where the samples came from, so we can't make any conclusions at all about their source or the identity of the fragments involved. Just because two fragments in different lanes are of the same size does not mean that they are the same fragment. That something is, for instance, 400 bp long does not serve as an identifier of that fragment. There are, quite literally, 6.668 x 10²⁴⁰ different DNA fragments of 400 bp possible.

Click on the blue link on top of that post and it will redirect you to the question I posted, it was about meiosis and chromosomes, relating to the question I just recently posted about why meiosis can occur with the absence of chromosomes (the question I attached in the link says that meiosis cannot occur)

But yeah I get the gel electrophoresis one, cheers xD