VCE Biology Question Thread

[Gogo14]

Can someone please answer help explain where I went wrong in these questions? For the chromosome number question, shouldn't it be 14 still because after S phase, the chromosomes have doubled, but are still attached together.
Thanks I really appreciate those who answer my posts
1. http://imgur.com/8IJuQzJ
2. http://imgur.com/tF82YLv
3. http://imgur.com/uxutPAR

[The Usual Student]

Can someone please answer help explain where I went wrong in these questions? For the chromosome number question, shouldn't it be 14 still because after S phase, the chromosomes have doubled, but are still attached together.
Thanks I really appreciate those who answer my posts
1. http://imgur.com/8IJuQzJ
2. http://imgur.com/tF82YLv
3. http://imgur.com/uxutPAR

forgive me these may be out of order
1) even if you duplicate a chromosome it still counts as TWO chromosomes and not just one. EVEN if they are identical!
So 14 x 2 = 28
I can elaborate more if you want
2) i think A should be right for the nonsense mutation one....
double check that answer since it seems a bit dodgey
BTW your answers are Blue and the right ones are red yeah?

[Butterflygirl]

Guys, if a question asks to discuss signal transduction of a specific hormone, do I only mention: The binding on the signalling molecule to receptor causes a signal cascade?

and not the response?

Thankyou!

[AhNeon]

For that same question (7c 2015), when it says 'identical genetic sequence', what exactly is it referring to? The RNA (molecule S)?
Also, I though that when a rregulatory protein/represser proteins attaches to the operator sequence, translation of the respective gene is inhibited, essentially turning the gene 'off', is this correct?
Like is it supposed to be that the protein produced due to the GC hormone binds to repressors on different gene operator sequences, thus allowing for the expression of different proteins-is that what the answer basically says?
Sorry for this, nerves kicking in and i basically had to learn the whole bio content in the last month, skipped regulatory genes and stuff

[Butterflygirl]

Why would further exposure to the allergen lead to more severe response?

Is there memory cells involved?

[Gogo14]

forgive me these may be out of order
1) even if you duplicate a chromosome it still counts as TWO chromosomes and not just one. EVEN if they are identical!
So 14 x 2 = 28
I can elaborate more if you want
2) i think A should be right for the nonsense mutation one....
double check that answer since it seems a bit dodgey
BTW your answers are Blue and the right ones are red yeah?

thank you
1) even if the chromosome is duplicated, shouldn't it still be 1 piece of DNA still because the chromatids are still attached to the kinetochore?
2) Yep my answer is blue and the right one is red. Thanks

[The Usual Student]

thank you
1) even if the chromosome is duplicated, shouldn't it still be 1 piece of DNA still because the chromatids are still attached to the kinetochore?
2) Yep my answer is blue and the right one is red. Thanks

what exam was this?
And nah a duplicated chromosome is considered a new chromosomes even if they are both structurally attached
hence two sister chromatids that are bound by the centromere are considered two different chromosomes.

[AhNeon]

Why would further exposure to the allergen lead to more severe response?

Is there memory cells involved?

I'd assume its because more IgE antibodies are embedded in mast cells, thus providing the capacity for more cross links on more mast cells. This causes more histamine to be released and so on

[Butterflygirl]

Also, whats the definition for transduction?

VCAA mentions secondary messengers but not all signalling molecules involve secondary messengers (lipid-based)?

[carlyjames]

Can you dot point your answers in the bio exam? or is that too informal?

[QueenSmarty]

Can you dot point your answers in the bio exam? or is that too informal?

Yes, you can dot point your answers. VCAA actually prefers dot points because it's easier to mark.

[hodang]

Hey guys!
Does facilitated diffusion involve carrier proteins or protein channels?

[The Usual Student]

Hey guys!
Does facilitated diffusion involve carrier proteins or protein channels?

both

[sweetcheeks]

Why would further exposure to the allergen lead to more severe response?

Is there memory cells involved?

To give a bit of background. Allergies are caused by antigens binding to special IgE antibodies that are on the surface of mast cells. When the binding occurs, it initiates the release of histamines. These antibodies are produced by B cells, which become either plasma B cells or memory B cells. When the allergen has a subsequent reoccurrence, both the mast cells and B memory cells are activated. The B memory cells undergo replication and differentiation, with plasma cells being produced as well as more memory cells. The amount of memory cells produced is higher than the initial amount.

What this means is that the plasma cells produce more antibodies that can bind to mast cells, resulting in more mast cells that are capable of responding to the antigen. Each time the allergen is encountered, there is a higher amount of antibodies produced, which can bind to more mast cells.

It is a similar principle to reinfection of pathogens (vaccination is a good example, where the initial response is low, but each subsequent infection has a higher response)

[QueenSmarty]

Do you guys think the exam this year is going to be hard?