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Author Topic: VCE Biology Question Thread  (Read 3571505 times)  Share 

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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9480 on: October 24, 2017, 10:06:17 pm »
+2
How much and how detailed do we need to know about BMP4 and master genes? There seems to be heaps of questions on this on the prac exams...

From the study design:
• the evolution of novel phenotypes arising from chance events within genomes, specifically sets of genes that regulate developmental processes and lead to changes in the expression of a few master genes found across the animal phyla, as demonstrated by the expression of gene BMP4 in beak formation of the Galapagos  finches and jaw formation of cichlid  fish in Africa.


It is a fairly large dot point but it is mostly about BMP4 as an example of master control genes. I would say you should definitly know:
-What BMP4 does
-That it leads to very fast divergent evolution (called adaptive radiation)
-That mutations occur in the genes coding for regulatory proteins that control its expression NOT in the BMP4 gene itself
-The differences seen due to more/less/early/late in Darwins finches and cichlids

EDIT: typo
« Last Edit: October 24, 2017, 10:14:26 pm by PhoenixxFire »
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areeb008

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Re: VCE Biology Question Thread
« Reply #9481 on: October 24, 2017, 10:21:19 pm »
+1
Hey guys for question 20 attached couldn't the answer also be B (correct answer is A) since mast cells are a type of leukocyte and are thus produced by the bone marrow which is a primary lymphoid organ? This was a question on 2013 vcaa if anyone wanted to know.

K888

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Re: VCE Biology Question Thread
« Reply #9482 on: October 24, 2017, 10:46:36 pm »
+3
Hey guys for question 20 attached couldn't the answer also be B (correct answer is A) since mast cells are a type of leukocyte and are thus produced by the bone marrow which is a primary lymphoid organ? This was a question on 2013 vcaa if anyone wanted to know.
Whilst technically true, I'd imagine it's not the answer because as far as I know, mast cells originate as haematopoietic progenitor cells(?), and don't fully differentiate into mast cells until they reach the connective tissue and other places they reside in. So, they're not actually technically mast cells when they're being produced in the bone marrow. :)

If anyone has a better/more detailed explanation, please provide!

smamsmo22

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Re: VCE Biology Question Thread
« Reply #9483 on: October 24, 2017, 10:49:01 pm »
0
Hi, I had a couple of random bio 3/4 questions that I haven't been able to find definitive answers to:

1. Regarding the BMP4 protein/gene (obviously this is new to the study design but I thought I may as well ask if you knew much about it), I read in a textbook that it was a master control regulatory gene, which codes for the protein BMP4, which is a signalling protein that regulates the expression of multiple structural genes that define distinctive characteristics such as beaks, jaws etc. Thus, mutations to the BMP4 gene result in the novel variations of these traits due to altered expression of the BMP4 protein... is this correct? I recently came across a source that said the BMP4 protein was the same in different organisms, hence the mutations did not occur to the BMP4 gene but a different regulatory gene that regulates BMP4 gene expression? I am aware that may not make any sense... but this confused me as it sounded like a regulatory gene regulating a master regulatory gene... If anyone could clarify BMP4 gene, the function of its protein product BMP4, and where these mutations occur, that would be awesome

2. In the allergic response, the production of (igE) antibodies is stimulated by the entry of an allergen to the body. Does this mean our body contains B cells/antibodies that are specific to and activated by normally harmless antigens? Or only in some people? The initiation of the allergic response when the allergen is identified is confusing me a bit.

3. Is there a definitive/worth noting difference between selective agent and selection pressure? I've read that they are separate (i.e. a selective agent inflicts a selection pressure on an environment), but when looking for examples of either they usually give the same factors, such as disease or predation. Is there a difference and would anyone be able to demonstrate this with clear examples?

4. Finally, this isn't so much to do with the course but I've gotten different responses to this question. It was on the VCAA sample exam, regarding whether raw data or averaged data should be used when drawing conclusion from experiment results. I believe you said to go with raw data, and I was just wondering why? It would've been my initial response too but I had a teacher tell me and a practice exam lean towards use of averaged values.

Thanks heaps!!
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areeb008

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Re: VCE Biology Question Thread
« Reply #9484 on: October 24, 2017, 10:51:17 pm »
0
Whilst technically true, I'd imagine it's not the answer because as far as I know, mast cells originate as haematopoietic progenitor cells(?), and don't fully differentiate into mast cells until they reach the connective tissue and other places they reside in. So, they're not actually technically mast cells when they're being produced in the bone marrow. :)

If anyone has a better/more detailed explanation, please provide!

ahh thanks man!! had no idea

areeb008

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Re: VCE Biology Question Thread
« Reply #9485 on: October 24, 2017, 11:07:41 pm »
+1
Hi, I had a couple of random bio 3/4 questions that I haven't been able to find definitive answers to:

1. Regarding the BMP4 protein/gene (obviously this is new to the study design but I thought I may as well ask if you knew much about it), I read in a textbook that it was a master control regulatory gene, which codes for the protein BMP4, which is a signalling protein that regulates the expression of multiple structural genes that define distinctive characteristics such as beaks, jaws etc. Thus, mutations to the BMP4 gene result in the novel variations of these traits due to altered expression of the BMP4 protein... is this correct? I recently came across a source that said the BMP4 protein was the same in different organisms, hence the mutations did not occur to the BMP4 gene but a different regulatory gene that regulates BMP4 gene expression? I am aware that may not make any sense... but this confused me as it sounded like a regulatory gene regulating a master regulatory gene... If anyone could clarify BMP4 gene, the function of its protein product BMP4, and where these mutations occur, that would be awesome

2. In the allergic response, the production of (igE) antibodies is stimulated by the entry of an allergen to the body. Does this mean our body contains B cells/antibodies that are specific to and activated by normally harmless antigens? Or only in some people? The initiation of the allergic response when the allergen is identified is confusing me a bit.

3. Is there a definitive/worth noting difference between selective agent and selection pressure? I've read that they are separate (i.e. a selective agent inflicts a selection pressure on an environment), but when looking for examples of either they usually give the same factors, such as disease or predation. Is there a difference and would anyone be able to demonstrate this with clear examples?

4. Finally, this isn't so much to do with the course but I've gotten different responses to this question. It was on the VCAA sample exam, regarding whether raw data or averaged data should be used when drawing conclusion from experiment results. I believe you said to go with raw data, and I was just wondering why? It would've been my initial response too but I had a teacher tell me and a practice exam lean towards use of averaged values.

Thanks heaps!!

For your first one, since BMP4 is a highly conserved protein i don't think a mutation in the gene would alter the function/shape of the protein, but likely cause changes in the level of expression of it which then causes variation in finches beaks and levels of bone development. These mutations would  also occur most likely directly in the coding sequences of the bmp4 gene, but I'm not too sure about that one! As for function the BMP4 gene is a master gene that basically through the expression of its protein influences the expression of a number of different genes which control cell differentiation, thereby influencing width and depth of the beaks- high levels of bmp4 protein mean wider and deeper beaks, whereas low levels of bmp4 normally cause narrower and shallower beaks. Hope if helps !!

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9486 on: October 24, 2017, 11:12:38 pm »
+4
1. According to Douchy AKA Edrolo guy AKA podcast guy the mutations occur in the gene that regulates expression of the BMP4 gene. Your confusion may be due to textbooks/teachers calling this the BMP4 regulatory gene, but it is not the BMP4 gene.

2. IgE antibodies bind to mast cells. They only cause the mast cells to degranulate (release histamine) when they cross link (2 antibodies bind to the same antigen) This normally only occurs when a big pathogen is present eg. A worm (parasite). An allergic response occurs when too many IgE antibodies are produced, meaning too many are bound to mast cells, meaning a small pathogen eg. Pollen. Can bind to 2 antibodies (as they are located closer together) causing the mast cell to degranulate when it shouldn't.
Not sure about the specificity part, only antibodies against self antigens are destroyed in maturation so it stands to reason that there would be antibodies capable of binding to allergens by random chance.

3. It's a technical difference:
Selective agent -the one who enforces the selection pressure eg. Bird, human
Selection pressure - something that favours some individuals over others eg. Predation, hunting

4. I would say averaged data is better as it makes the results more accurate. - It reduces the effect of mistakes (that only occurred in one repetition) on the overall results.

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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9487 on: October 24, 2017, 11:17:20 pm »
0
For your first one, since BMP4 is a highly conserved protein i don't think a mutation in the gene would alter the function/shape of the protein, but likely cause changes in the level of expression of it ......These mutations would  also occur most likely directly in the coding sequences of the bmp4 gene....

Mutations in the coding sequences of a gene will not alter the rate of expression of that same gene.
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TheBigC

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Re: VCE Biology Question Thread
« Reply #9488 on: October 25, 2017, 01:01:04 am »
+1
Hi, I had a couple of random bio 3/4 questions that I haven't been able to find definitive answers to:

1. Regarding the BMP4 protein/gene (obviously this is new to the study design but I thought I may as well ask if you knew much about it), I read in a textbook that it was a master control regulatory gene, which codes for the protein BMP4, which is a signalling protein that regulates the expression of multiple structural genes that define distinctive characteristics such as beaks, jaws etc. Thus, mutations to the BMP4 gene result in the novel variations of these traits due to altered expression of the BMP4 protein... is this correct? I recently came across a source that said the BMP4 protein was the same in different organisms, hence the mutations did not occur to the BMP4 gene but a different regulatory gene that regulates BMP4 gene expression? I am aware that may not make any sense... but this confused me as it sounded like a regulatory gene regulating a master regulatory gene... If anyone could clarify BMP4 gene, the function of its protein product BMP4, and where these mutations occur, that would be awesome

2. In the allergic response, the production of (igE) antibodies is stimulated by the entry of an allergen to the body. Does this mean our body contains B cells/antibodies that are specific to and activated by normally harmless antigens? Or only in some people? The initiation of the allergic response when the allergen is identified is confusing me a bit.

Thanks heaps!!

Okay, lots of stuff here.. good questions.

1. Now, the first point, it is true that THE gene that regulates the expression of the BMP4 gene undergoes mutations to give rise to the novel phenotypes and NOT the BMP4 gene itself... if you look at this from a logical standpoint it makes perfect sense:
- A mutation in the BMP4 gene itself would NOT alter its level of expression, however, would alter the BMP4 protein... resulting in it having a different primary structure and concomitantly a different tertiary structure. This would change or eradicate its functionality (which obviously is not occurring in cichlid fish OR the Galapagos finches).
- Instead, a master regulatory gene that REGULATES the expression of BMP4 is altered, resulting in differential expression of the BMP4 gene, producing the novel phenotypes associated with beak width/depth, and the jaw of cichlid fish (short, heavy etc.).....

2. For the second question, if we consider an allergic response, an allergen or antigen enters the body of an individual, is engulfed and digested by phagocytes, of which then being presented to naive B and T cells... these cells, therefore, to react with the antigen or allergen must have complementary receptors toward it.. whereby producing IgE in response. As far as if only some people have it or everyone has cells with specific receptors to the allergen... I honestly couldn't say (sounds like a question beyond the scope of the course.. but I am sure that with some research online you'd find something!).


PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9489 on: October 25, 2017, 04:09:31 am »
0

2. For the second question, if we consider an allergic response, an allergen or antigen enters the body of an individual, is engulfed and digested by phagocytes, of which then being presented to naive B and T cells... these cells, therefore, to react with the antigen or allergen must have complementary receptors toward it.. whereby producing IgE in response.

Not entirely correct, this happens during sensitisation, not during an allergic response. Allergic responses only involve innate immunity (the release of histamine), they are triggered by the cross linking of IgE antinbodies that have bound to a mast cell.
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vox nihili

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Re: VCE Biology Question Thread
« Reply #9490 on: October 25, 2017, 07:00:37 am »
+2

1. According to Douchy AKA Edrolo guy AKA podcast guy the mutations occur in the gene that regulates expression of the BMP4 gene. Your confusion may be due to textbooks/teachers calling this the BMP4 regulatory gene, but it is not the BMP4 gene.

2. IgE antibodies bind to mast cells. They only cause the mast cells to degranulate (release histamine) when they cross link (2 antibodies bind to the same antigen) This normally only occurs when a big pathogen is present eg. A worm (parasite). An allergic response occurs when too many IgE antibodies are produced, meaning too many are bound to mast cells, meaning a small pathogen eg. Pollen. Can bind to 2 antibodies (as they are located closer together) causing the mast cell to degranulate when it shouldn't.
Not sure about the specificity part, only antibodies against self antigens are destroyed in maturation so it stands to reason that there would be antibodies capable of binding to allergens by random chance.

3. It's a technical difference:
Selective agent -the one who enforces the selection pressure eg. Bird, human
Selection pressure - something that favours some individuals over others eg. Predation, hunting

4. I would say averaged data is better as it makes the results more accurate. - It reduces the effect of mistakes (that only occurred in one repetition) on the overall results.

These answers are excellent. You’re knowledge is pretty freaky given where you’re at. One very minor point:

2. Allergens aren’t really pathogens. You should avoid calling them that, because the whole point of allergy is that it’s an inappropriate response to something that isn’t a pathogen.

4. These questions were originally DMed to me (good on you for posting smamso22).
The question about raw vs average data is a reference to SAQ1 (I think?) from the practice exam.
Raw data are always better than averages. This is because there is inherently more information in raw data that you just don’t have access to when you average it.
In the case of that question, which I can’t remember the exact details of off the top of my head, averaging it effectively eliminated any difference between the group, despite there being one aberrant group that was skewing the results.
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vox nihili

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Re: VCE Biology Question Thread
« Reply #9491 on: October 25, 2017, 07:08:24 am »
+1

These answers are excellent. You’re knowledge is pretty freaky given where you’re at. One very minor point:

2. Allergens aren’t really pathogens. You should avoid calling them that, because the whole point of allergy is that it’s an inappropriate response to something that isn’t a pathogen.

4. These questions were originally DMed to me (good on you for posting smamso22).
The question about raw vs average data is a reference to SAQ1 (I think?) from the practice exam.
Raw data are always better than averages. This is because there is inherently more information in raw data that you just don’t have access to when you average it.
In the case of that question, which I can’t remember the exact details of off the top of my head, averaging it effectively eliminated any difference between the group, despite there being one aberrant group that was skewing the results.

Some more thoughts on the question:

Potentially VCAA would accept average or raw as long as you can justify it.

The question asks you about valid conclusions. This implies that they reflect what the “true” answer is. If you use the average, I would argue that you can’t do that because your conclusion would be “there is no change in the percentage of oxygen therefore respiration does not occur”, which is wrong.
However, if you use the raw data your conclusion would be the opposite. In all bar one group, the concentration of oxygen decreased therefore respiration occurred.

You can see clearly that group 2 is an aberration. This is useful information, because it tells us that groups 1, 3 and 4 tell a different story. If you took the average, you lose that vital information.






VCAA have never asked a question like this before, so it’s hard to tell where they’ll go on this. PhoenixFire’s point is compelling and, critically, references the knowledge you need to have; however, common sense dictates that raw is better and on that basis I think it should be correct.
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grestal

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Re: VCE Biology Question Thread
« Reply #9492 on: October 25, 2017, 07:11:30 am »
0
hi,
can someone please explain the techniques in identifying a pathogen (diagnosing infectious disease)
e.g. ELIZA, PCR, bacteria culture, how do they actually use these techniques to come to any conclusion.

thanks
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vox nihili

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Re: VCE Biology Question Thread
« Reply #9493 on: October 25, 2017, 07:35:48 am »
+4
PCR: you should already know how that works, so I won’t go into the details. You just get a body sample and see if you can amplify bacterial/viral DNA by using primers specific to that DNA.
ELISA: again, won’t go into too many details. Basically what you do is you get antibodies specific to a pathogen and put them on a slide. Then you get a sample from somebody’s body. If the pathogen is present, the pathogen will bind to the antibodies and will light up (don’t worry about how this works).
Culture: get a sample, chuck it on a dish and see if bacteria grow. This is by far the most common for bacteria, whereas PCR or ELISA are used more for viruses.
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smamsmo22

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Re: VCE Biology Question Thread
« Reply #9494 on: October 25, 2017, 10:45:40 am »
+1
1. According to Douchy AKA Edrolo guy AKA podcast guy the mutations occur in the gene that regulates expression of the BMP4 gene. Your confusion may be due to textbooks/teachers calling this the BMP4 regulatory gene, but it is not the BMP4 gene.

2. IgE antibodies bind to mast cells. They only cause the mast cells to degranulate (release histamine) when they cross link (2 antibodies bind to the same antigen) This normally only occurs when a big pathogen is present eg. A worm (parasite). An allergic response occurs when too many IgE antibodies are produced, meaning too many are bound to mast cells, meaning a small pathogen eg. Pollen. Can bind to 2 antibodies (as they are located closer together) causing the mast cell to degranulate when it shouldn't.
Not sure about the specificity part, only antibodies against self antigens are destroyed in maturation so it stands to reason that there would be antibodies capable of binding to allergens by random chance.


Thank you for your answers!! Just a couple of follow up questions for clarification;
1. So now I understand that the mutations to the regulator gene for the master gene BMP4, are what alters the expression of BMP4 protein (not the actual makeup of the protein) and hence produces novel phenotypes. (Thanks!) Am I still correct in saying BMP4 gene is a master control regulatory gene, and that BMP4 protein is a transcription factor that is able to regulate the expression of a suite of structural genes? i.e. there is another regulatory gene (that mutates) that regulates expression of the master regulatory gene BMP4, that regulates the expression of phenotypes?

2. I think I understand the triggering of the allergen of an allergic response, I am just confused about how the initial production of IgE antibodies against the allergen comes about (sensitisation, I should've called it) when it enters the body. I was just confused by the concept that we had B cells that contained/produced specific antibodies against normally harmless allergens? Is that right? And how this only occurs in some people.
Thanks so much!
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