VCE Biology Question Thread

[dankfrank420]

Not sure what you're asking above, but I think DNA is referred to as universal because the same base sequence codes for the same amino acids in almost all organisms. It's referred to as redundant because the same amino acid can be specified by more than one codon (a codon is a sequence of three bases).

Hope that helps you.

Yeah my question was poorly worded, but thanks this really helped me.

[DJA]

Could someone go through the whole idea of linked genes in DETAIL with examples if you can be bothered?
-> and also how to notate linked sets of alleles and all that kind of stuff - screws with my head

Much love if you could - I still can't get my head around the whole things

[dankfrank420]

Could someone go through the whole idea of linked genes in DETAIL with examples if you can be bothered?
-> and also how to notate linked sets of alleles and all that kind of stuff - screws with my head

Much love if you could - I still can't get my head around the whole things

Linked genes are genes that have loci on the same chromosome.As such, they tend to be inherited together more often unless crossing-over/recombination at Prophase I of meiosis occurs. They are denoted with a "fraction", with the "numerator" being one chromosome and the "denominator" being the other chromosome. For example, instead of AaBb it would be represented with AB/ab or Ab/aB( depends on which alleles are 'paired' on the same chromosome.)

I'm not sure what examples you're after, but just remember linked genes tend to be inherited more often together, as they are on the same chromosome.

[TimewaveZero]

How is a nerve impulse initially started? I mean, I know how a nerve impulse is transmitted across a synaptic cleft to trigger another action potential in the post synaptic nerve, but how is the first one started? For example, how does me touching a hot plate trigger a nerve impulse?

[vox nihili]

How is a nerve impulse initially started? I mean, I know how a nerve impulse is transmitted across a synaptic cleft to trigger another action potential in the post synaptic nerve, but how is the first one started? For example, how does me touching a hot plate trigger a nerve impulse?

In an interneurone for example, or a motor neurone, an action potential is started when neurotransmitters are shot across the synapse. These open up sodium channels and voilą, you have an AP

[TimewaveZero]

In an interneurone for example, or a motor neurone, an action potential is started when neurotransmitters are shot across the synapse. These open up sodium channels and voilą, you have an AP

How is a nerve impulse initially started? I mean, I know how a nerve impulse is transmitted across a synaptic cleft to trigger another action potential in the post synaptic nerve, but how is the first one started? For example, how does me touching a hot plate trigger a nerve impulse?

Yes, thank you for a response, but I was referring to how it occurs in the first place... how is the initial response generated.. in response to an event... that requires a response... (that was badly worded I know, I don't know how else to put it)

[anat0my]

What would be the selection pressure for the development of larger craniums?

[soNasty]

Yes, thank you for a response, but I was referring to how it occurs in the first place... how is the initial response generated.. in response to an event... that requires a response... (that was badly worded I know, I don't know how else to put it)

Im pretty sure neurotransmitters (eg. acetylcholine) can be synthesised within the axon terminal with the aid of enzymes. This would obviously be the first stage of synaptic transmission.

[Rishi97]

guys, I'm really struggling with immunity. I'm getting all the questions wrong on past exam papers. Is anyone willing to pm me their notes or any resources that will help?
Much much much appreciated

Thanks

[vox nihili]

guys, I'm really struggling with immunity. I'm getting all the questions wrong on past exam papers. Is anyone willing to pm me their notes or any resources that will help?
Much much much appreciated

Thanks

Pretty sure I put up some immunology notes at some point on the ATARNotes thingy, so have a squiz there

[anat0my]

What would be the selection pressure for the development of larger craniums?

Bump!

Also, does anyone know where to find Lisachem 2006 unit 4 solutions? Thanks!

[grannysmith]

Methyl jasmonate is very volatile and is able to act as an attractant to the predators of the herbivore insect (which browses on the plant that releases the methyl jasmonate). This acts in a similar way to a pheromone.

How is the action of methyl jasmonate similar and different from a pheromone?


Would a plausible similarity be that is is released into the external environment of the plant, as pheromones are also released into the external environment of the organism?

The suggested answers does not include the above; it says the similarity is that is affects other living organisms.

[ValiantIntellectual]

Hi, I have being getting a head start on vce bio and just want to ask, since all macromolecules can be split from their polymers through the addition of water ( hydrolysis) are all polymers soluble?

[grannysmith]

Another question.

What is the role of T helper cells in the human immune response?

My answer:

Spoiler

They initiate the cell-mediated response by releasing cytokines which activate specific cytotoxic T cells. They also activate the humoral response by releasing cytokines which stimulate specific B cells to undergo clonal expansion, thus proliferating and differentiating into antibody-producing plasma B-cells and memory B-cells.

Suggested answer:

Spoiler

Macrophages that have ingested microorganisms display antigens on their surface that the T helper cell recognises. B cells that bind to the same macrophage are helped to differentiate into plasma cells that produce antibodies.

The suggested answers seem off as it does not address the cell-mediated response - and I never knew that B cells bind with macrophages? O.o
I always thought they recognise and bind directly to a specific antigen, and are stimulated into proliferating and differentiating with the aid of T helper cells?

This is a STAV paper btw.

[grannysmith]

Hi, I have being getting a head start on vce bio and just want to ask, since all macromolecules can be split from their polymers through the addition of water ( hydrolysis) are all polymers soluble?

Solubility is also influenced by the size of a molecule; for example, starch is relatively insoluble even though it is a polymer of glucose. That's why plants use it as an energy reserve. Also, fibrous proteins are insoluble, although they are macromolecules.

Usually an enzyme is required to hydrolyse a polymer, and the addition of water itself would not be able to hydrolyse all polymers.

So no, not all polymers are soluble.