VCE Biology Question Thread

[vox nihili]

How much depth do I need to study for plant hormones?
Can someone also explain to me why the answer is B and not C.
Thank-you

Answer is definitely B.

The difference comes down to which one is the amylase mixed with inhibitor and which is amylase at 20°C. The easiest of these two to identify is the inhibitor, so we'll just work on that.

If amylase is mixed with inhibitor, the amylase shouldn't work. One would therefore expect to see a flat line along the x-axis or a line that only very barely gets off the axis. Depending on the nature of the inhibitor, it is also possible that the amount of maltose would never reach its maximum. This appears to be what they're illustrating here. The graph that corresponds with this is graph S

Is it true that even if you cook meat infected with tapeworms very well, you can still become infected with it if you consume it?

Not beyond the realm of possibility, though it really shouldn't happen. Depends on how hot the meat gets and what temperature the worms can withstand.

[Biology24123]

How much depth do I need to study for plant hormones?
Can someone also explain to me why the answer is B and not C.
Thank-you

Know that the same hormone can cause a different response in different parts of the plant but not any specific names of plant hormones or their function

[sushibun]

Answer is definitely B.

The difference comes down to which one is the amylase mixed with inhibitor and which is amylase at 20°C. The easiest of these two to identify is the inhibitor, so we'll just work on that.

If amylase is mixed with inhibitor, the amylase shouldn't work. One would therefore expect to see a flat line along the x-axis or a line that only very barely gets off the axis. Depending on the nature of the inhibitor, it is also possible that the amount of maltose would never reach its maximum. This appears to be what they're illustrating here. The graph that corresponds with this is graph S

Not beyond the realm of possibility, though it really shouldn't happen. Depends on how hot the meat gets and what temperature the worms can withstand.

Thanks!
Regarding the worm question I attached exam question about it and it says the least effective measure in preventing the children from contracting Tapeworms on a sheep farm is A) well cooked lamb
Why? D:

[sushibun]

Know that the same hormone can cause a different response in different parts of the plant but not any specific names of plant hormones or their function

Oh okay so auxins in stems, shoots and roots
gibberellins in fruit and germinating seeds?
Cytokinins in areas a lot of cell division such as coleoptiles
Abscisic Acid in stems
Ethylene in fruit and damaged areas of plant
I should revise this. Thanks!

[Biology24123]

Oh okay so auxins in stems, shoots and roots
gibberellins in fruit and germinating seeds?
Cytokinins in areas a lot of cell division such as coleoptiles
Abscisic Acid in stems
Ethylene in fruit and damaged areas of plant
I should revise this. Thanks!

You don't need to know any of that

MOD EDIT: just fixed up so the quote worked all right

[warya]

Do we need to know the different types of stem cells, like totipotent, embryonic etc?

[Biology24123]

Do we need to know the different types of stem cells, like totipotent, embryonic etc?

Yes, and advantages of adult and embryonic stem cells

[cosine]

According to the course it's mainly the cell mediated response

So for the sake of VCE, in autoimmune diseases, there can be both cell-mediated AND humoral responses

But in transplanted rejection, there is only cell-mediated response, right?

[tashhhaaa]

do we need to know stuff like different classifications of bacteria or any obscure details about viruses, prions etc?

[cosine]

do we need to know stuff like different classifications of bacteria or any obscure details about viruses, prions etc?

Just to reiterate my own knowledge:

Bacteria: Cellular pathogens, unicellular - only one cell organisms. They have one single circular chromosome that is not in the nucleus, because they lack nuclei. But they also have many circular plasmids as additional genes, which are usually used for resistance and defence mechanisms.

Viruses: Non-cellular pathogens that can invade host cells in mammals via invasion of host cells - where it uses the host cell machinery and injects its own viral genome into the normal DNA to reproduce more copies of itself, assembles into the viral particles and then they lyse the host cell upon leaving. There are also bacteriophages that infect bacterial cells. These viruses do not enter the bacteria but instead inject their viral genome by attaching to the membranes.

Prions: Non-cellular pathogens that are defected proteins. They defect other proteins by contact, and change their shape to their own defective shape. Usually found in the brain cells/tissue.

Thats all you need to know.

However, I have a question of my own. When viruses invade host cells and reproduce more viral particles, does the host cell eventually lyse, or do the viruses just leave the cell?

[tashhhaaa]

Just to reiterate my own knowledge:

Bacteria: Cellular pathogens, unicellular - only one cell organisms. They have one single circular chromosome that is not in the nucleus, because they lack nuclei. But they also have many circular plasmids as additional genes, which are usually used for resistance and defence mechanisms.

Viruses: Non-cellular pathogens that can invade host cells in mammals via invasion of host cells - where it uses the host cell machinery and injects its own viral genome into the normal DNA to reproduce more copies of itself, assembles into the viral particles and then they lyse the host cell upon leaving. There are also bacteriophages that infect bacterial cells. These viruses do not enter the bacteria but instead inject their viral genome by attaching to the membranes.

Prions: Non-cellular pathogens that are defected proteins. They defect other proteins by contact, and change their shape to their own defective shape. Usually found in the brain cells/tissue.

Thats all you need to know.

However, I have a question of my own. When viruses invade host cells and reproduce more viral particles, does the host cell eventually lyse, or do the viruses just leave the cell?

thank you!

I think the host cell lyses, someone please correct me if this is wrong
however, I know that if the virions build up in a cell they cause it to burst.

I was confused about this as well, because if the virus needs the host cell to reproduce, why would it lyse it? o.O
edit: realised that it lyses the host cell to release the copies of the virus, which then infect other host cells/cycle continues?

If you have Nature of Biology, refer to the diagram on page 206
It's for bacteriophages but it should still apply

[vox nihili]

thank you!

I think the host cell lyses, someone please correct me if this is wrong
however, I know that if the virions build up in a cell they cause it to burst.

I was confused about this as well, because if the virus needs the host cell to reproduce, why would it lyse it? o.O
edit: realised that it lyses the host cell to release the copies of the virus, which then infect other host cells/cycle continues?

If you have Nature of Biology, refer to the diagram on page 206
It's for bacteriophages but it should still apply

Some don't actually lyse the cells. Generally though lysis is a strategy that viruses use to get out of the cell. They need to be able to get around. Also, there are so many cells available for the viruses that they can afford to push the host cell machinery so hard that it kills them.

[cosine]

For this question, i just want to grasp a conceptual understanding of it.

It says that the blood samples were taken from the victim in which the blood had been deposited on the victim during the crime scene. DNA was extracted from white blood cells in each of the blood samples and electrophoresis of the samples was carried out.

You know how in each well there are multiple fragments, are these fragments meant to be of the same gene locus? For example, you see well 2 where it is the crime scene samples, those fragments correspond mostly to the suspect 2, but when the geneticists took the blood sample from the suspect 2, would they have taken the DNA sample from the same gene loci that they took from the crime scene sample to see whether or not the suspect would produce similar sized fragments of the same gene? Because the restriction enzyme that cuts the crime scene suspects samples would also cut the DNA of the actual suspect with the same number of fragments if it were the same loci? Also if this is the case too, do the other suspects have different sized lengths because they all have different alleles for the gene loci?

This whole theory could be incorrect because it is just my understanding of it, if it is incorrect, mind enlightening me with not the process of electrophoresis, but what samples are used from suspects? Because a question earlier on in the year asked what geneticists would do further to ensure that the suspect was indeed present during the crime scene, and the answer said that they should test another gene loci and see if the sample at the crime scene would match with the suspect's gene loci fragments. Any ideas?

Many thanks in advance.

Anyone willing to help a brother out?

[thushan]

I think you are confusing two concepts here - DNA fingerprinting and DNA profiling.

DNA fingerprinting --> chop samples of DNA with specific restriction enzymes --> gel electrophoresis of all samples --> compare fragmentation pattern

The concept is that different people will have different sites within their DNA where the restriction enzymes will cut. Therefore, they will have different sizes of fragments and therefore different fragmentation patterns. This question is likely referring to this technique.

DNA profiling --> perform PCR using specific DNA primers that are fluorescently labelled that will amplify specific STR loci --> perform gel electrophoresis to determine which alleles at each STR locus the person contains --> obtain the "genotype" at each of 9 STR loci

Restriction enzymes are involved with a DNA fingerprinting technique; STR loci are involved in DNA profiling.

[cosine]

I think you are confusing two concepts here - DNA fingerprinting and DNA profiling.

DNA fingerprinting --> chop samples of DNA with specific restriction enzymes --> gel electrophoresis of all samples --> compare fragmentation pattern

Yep with this one, all I am asking is whether or not the use a specific gene loci for all the suspects?

For example, if they use restriction enzymes that cut a specific recognition site on the DNA of the suspects, what if they cut different fragments on the suspect's DNA as compared to the crime scene DNA fragment? Wouldn't that result in no matches?