VCE Biology Questions Thread

BIOQ

Hi there. I was wondering if anyone would be able to explain how CRISPR CAS 9 defence system works in bacteria.

Smartiestarz

BIOQ
In bacteria CRISPR acts as a defence system by recognising foreign viral DNA sequences and incorporating it into the bacteria’s CRISPR sequence/genome as a “spacer” upstream of the PAM. This occurs as cas9 is able to cut the viral DNA at a specific sequence of nucleotides (restriction site) complementary to the nucletides of the short guide RNA
This allows the bacteria to have a memory of past viral infections such that in future if the same virus invades, a faster, stronger, greater response is triggered as the cas9 rapidly cuts the viral DNA inducing a mutation in it and preventing it from replicating, hence preventing viral infection/spread in the bacterium. The PAM a sequence of nucletides downstream of the gene of interest in the virus which helps cas9 differentiate between the virus as a “non self” molecule and the bacterias own CRISPR genome as being “self”

chemistry1111

does substrate bind to enzyme or enzyme binds to substrate?

chemistry1111

how do we explain anaerobic respiration? and also why is producing atp important in respiration

MM_7

Does the tracrRNA bind to the palindromic sequence on the CRISPR sequence or on the crRNA?

chemistry1111

Smartiestarz
do bacteriophages insert both DNA or RNA or just DNA?

Smartiestarz

Yes I think sme bacteriophages can insert RNA-not entirely sure though. It’s interesting actually cos Ive only heard of bacteriophages inserting viral DNA that forms a “spacer” as part of the CRISPR sequence/genome but you might wanna double check with your teacher 🙂

MinahilMehr

Hi all, can someone please explain to me in things like hayfever, does histamine cause watery eyes so that lysozymes in those "tears" can remove pollen (or other allergens)?

Moskva

Hello MinahilMehr!

In short, no, allergic responses are "overreactions" and do not have any real meaning or purpose.

chemistry1111

is a protein functional at tertiary or quartenary structure?

_sophiestudies_

chemistry1111 It is functional at both, but it must at least be at a tertiary structural level to be functional. All proteins must at least be a tertiary protein to function, but some will also have a quaternary structure and are a still functional (but not all functional proteins will have a quaternary structure).

Moskva

Hey chemistry1111!

Every protein has tertiary structure, no exceptions. 😉

NG900

Hello there,
Can someone please explain the process of attenuation in the regulatory mechanism of tryptophan?
Also, what are the key ideas that I should know about mtDNA in relation to the topic of evolution?

Kind regards 🙂

Moskva

Privet NG900!

Attenuation inhibits expression of the structural genes of the TrpOperon in conditions of mild-to-high concentration of loaded tryptophan tRNA.
There is a sequence of DNA located downstream of the promoter, and upstream of the structural genes, of the TrpOperon called the TrpLeader sequence. It contains two triplets, that when transcribed, become two codons (so mRNA) for tryptophan.
(Recall that transcription and translation occurs concurrently in prokaryotes)
When the ribosome reaches these two codons, it will stall in conditions of low loaded tryptophan tRNA -- and attenuation will not occur --, it will continue normally otherwise -- and attenuation will occur --.
Why you ask? This you don't really need to know in detail, but basically the time taken for the ribosome to translate those two codons will determine how the mRNA section ahead is folded. Different folding patterns will result in attenuation or not, depending [again, on the time the ribosome takes to reach it].

Apologies if I confused you haha 😅

NG900

Moskva thank you so much for your explanation.

bioho4

hi, can someone help me with questions 2e, 3c and all of question 9 from the 2022 vcaa sample exam? And is it just me or is this exam a lot harder than previous years vcaa exams? The question style seems skewed towards more "subjective" application questions instead of technical theory questions...

Moskva

bioho4

Hmmmm... I haven't done the 2022 sample yet, so I cannot assist you with that.

However on the latter point, I have heard that the chief VCAA assessor for VCE Biology is also a Psychology teacher. Which would explain your observation (VCE Psychology is a borderline English subject, where you have 10 mark questions with explicit mark allocations for paragraph and sentence structuring). It is just a rumour though, do not take it as fact.

If it is really true, I think it would be a shame.
VCE Biology's content is very enjoyable, possibly the best science in the VCE in terms of theory. However I think this "subjective application", style as you call it, is the incorrect approach taken by the assessors, the proper assessment approach for Biology, would be to test "technical application" where the same theory is mapped onto unfamiliar contexts (e.g. Enzyme theory for ribozymes... etc)...

chemistry1111

do we need to know about the signal transduction pathway and process??

Moskva

chemistry1111

No, this is for the next SD 😉

clazah

for the exam do we need to know the numbers of each input and output for photosynthesis and cellular respiration?

Moskva

clazah

Only for ATP.

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