VCE Biology Question Thread

[BakedDwarf]

Oh come on, what even is this...? Is this in the study design or not? If this is true then is it not wrong to say that meiosis results in the production of 4 gametes from germline cells?

This was my exact thought process when I got the question wrong. I was like 'What the fuck... meiosis in females doesn't result in 4 gametes?"

Did a bit of googling and it turns out that four gametes are produced, but two become bar bodies and the bulk of the nutrients of one of the gametes is transferred to the other one. Hence, females produce only one gamete per cell undergoing meiosis. (correct me if i'm wrong)

[warya]

is the survival value of the phenotype related to whether it is dominant or recessive?

[vox nihili]

This was my exact thought process when I got the question wrong. I was like 'What the fuck... meiosis in females doesn't result in 4 gametes?"

Did a bit of googling and it turns out that four gametes are produced, but two become bar bodies and the bulk of the nutrients of one of the gametes is transferred to the other one. Hence, females produce only one gamete per cell undergoing meiosis. (correct me if i'm wrong)

Yep, that's right but well and truly beyond VCE

[cosine]

Yep, that's right but well and truly beyond VCE

But that question was on the VCAA exam 2 for 2009

[pi]

Yep, that's right but well and truly beyond VCE

I definitely learnt about that in VCE bio though?

[Biology24123]

If homologous chromosomes cross over, then why doesnt crossing over occur in mitosis? Don't the homologous chromosomes also line up in the middle of the cell during mitosis too?

Mitosis is basically meiosis II. There are no homologous chromosomes

[vox nihili]

But that question was on the VCAA exam 2 for 2009

I definitely learnt about that in VCE bio though?

Hmmm that's interesting. It's not something that's covered in many of the textbooks. Most students I've worked with have never covered that level of detail. I daresay they wouldn't ask it again—particularly given the downsizing of the course in 2013—but better to be safe than to be sorry!

[cosine]

Mitosis is basically meiosis II. There are no homologous chromosomes

How are there no homologous chromosomes during mitosis? Don't the chromosomes form sister chromatids and then line up in the middle to be separated?

[Biology24123]

How are there no homologous chromosomes during mitosis? Don't the chromosomes form sister chromatids and then line up in the middle to be separated?

Yes, you are correct but it's they're not homologous chromosomes. Chromosomes don't pair up in mitosis, the individual chromosomes lineup in metaphase

[cosine]

Yes, you are correct but it's they're not homologous chromosomes. Chromosomes don't pair up in mitosis, the individual chromosomes lineup in metaphase

But the term homologous has nothing to do with the way they line up, homologous just means they belong to the same family, that is, they're the same. So why doesn't crossing over occur in mitosis, anyone know?

[vox nihili]

But the term homologous has nothing to do with the way they line up, homologous just means they belong to the same family, that is, they're the same. So why doesn't crossing over occur in mitosis, anyone know?

Because they don't pair up...

In meiosis I, homologous chromosomes pair up and it is these that are split. In mitosis, chromosomes randomly line up and the chromosomes are split in half. The proteins that facilitate the pairing up of homologous chromosomes in meiosis are not expressed in mitotic cells; therefore, homologous chromosomes don't associate.

[cosine]

Because they don't pair up...

In meiosis I, homologous chromosomes pair up and it is these that are split. In mitosis, chromosomes randomly line up and the chromosomes are split in half. The proteins that facilitate the pairing up of homologous chromosomes in meiosis are not expressed in mitotic cells; therefore, homologous chromosomes don't associate.

Cheers,

Can meiosis occur if an organism is monosomy ?

[tashhhaaa]

hey guys,

do we need to know about lysosomes or organelles not explicitly stated in the study design?

it's not on the FAQs thing so sorry for the annoying question but I have trouble interpreting what I actually need to know :s

[cosine]

How accurate is the attached image regarding inflammation and fever? (Neap 2009 answer)

Few questions:

1. Describe one possible form of an effective equine influenza vaccine?
Can it be said that if the viral genome is removed, the virus is attenuated and is unable to infect, but still will induce an immune response?

2. Explain how the vaccine would lead to an immune response in a horse?
This is exactly what I wrote:

The attenuated viruses will be engulfed by phagocytes such as macrophages and the antigenic fragments presented on MHC II markers. Specific helper T cells recognise these markers and become activated, then these helper T cells activate cytotoxic T cells to proliferate into effector and memory T cells. B cells are also activated when they present the same antigen on their MHC II markers to helper T cells and proliferate into plasma and memory B cells.

Their answer is also attached (second image). They have nothing mentioned about Cytotoxic T cells, anyone know why? How would I know not to include T cells in the answer? Is it bad that I actually did? Also, they go on about antibody production and pathogen neutralisation, is this required to be stated in the answer? Because the question says how the vaccine would lead to an immune response, but once again why did they not mention the activity of T cells?

[cosine]

hey guys,

do we need to know about lysosomes or organelles not explicitly stated in the study design?

it's not on the FAQs thing so sorry for the annoying question but I have trouble interpreting what I actually need to know :s

Yeh, not specifically but be safe, on a MC once the question asked an example of first line defence mechanism:

A. Lysosomes
B. Lysozymes
C. Antibodies
D. Forgot this one

Obviously here you needed to know the different between lysosomes (organelles that fuse with phagosomes to destroy the pathogens in the second line of defence in phagocytes) and lysozymes (enzymes secreted in tears as a first line of defence that kill bacteria)