VCE Biology Question Thread

[vcestressed]

If a question is asking to design a prac, would it be okay to write in dot point format or would writing in paragraphs make more sense?

[Quantum44]

If a question is asking to design a prac, would it be okay to write in dot point format or would writing in paragraphs make more sense?

I always use dot points for experimental design as they are not really asking you to explain the method, it's more just stating specific aspects of your experiment. I'd suggest looking at past examination reports (as most past exams had an experimental design question) to see what VCAA look for in answers.

[jem_]

Hello to the world of ATARNotes I'm having trouble defining the genetic code. My current understanding is that it's the sequence of bases in the DNA template strand, in which 3 bases (a codon) code for one genetic instruction (eg. start instructions, to add an amino acid or stop instructions). It also involves the key features of being redundant, non overlapping, and being almost, but not quite, universal. Is this pretty much it?
Thank you

[vcestressed]

Hello to the world of ATARNotes I'm having trouble defining the genetic code. My current understanding is that it's the sequence of bases in the DNA template strand, in which 3 bases (a codon) code for one genetic instruction (eg. start instructions, to add an amino acid or stop instructions). It also involves the key features of being redundant, non overlapping, and being almost, but not quite, universal. Is this pretty much it?
Thank you

Honestly, your definition has everything that's needed.

[Quantum44]

Hello to the world of ATARNotes I'm having trouble defining the genetic code. My current understanding is that it's the sequence of bases in the DNA template strand, in which 3 bases (a codon) code for one genetic instruction (eg. start instructions, to add an amino acid or stop instructions). It also involves the key features of being redundant, non overlapping, and being almost, but not quite, universal. Is this pretty much it?
Thank you

You are correct that DNA is redundant, non-overlapping and universal, however you don't actually refer to three bases on the DNA strand as a codon. Three bases on a DNA strand are called a triplet, while three bases on an mRNA strand (after RNA processing) are called a codon and of course, the three bases on a tRNA are called an anticodon.

You also have to understand that not all of the DNA bases actually code for any amino acids. Only exon regions of the DNA are maintained in transcription so DNA in the intron regions are not expressed in the phenotype. Interestingly enough this is why we can analyse STRs in the intron regions as mutations that accumulate in the introns are not under any selection pressures and hence are highly unique to individuals.

[vox nihili]

You are correct that DNA is redundant, non-overlapping and universal, however you don't actually refer to three bases on the DNA strand as a codon. Three bases on a DNA strand are called a triplet, while three bases on an mRNA strand (after RNA processing) are called a codon and of course, the three bases on a tRNA are called an anticodon.




You also have to understand that not all of the DNA bases actually code for any amino acids. Only exon regions of the DNA are maintained in transcription so DNA in the intron regions are not expressed in the phenotype. Interestingly enough this is why we can analyse STRs in the intron regions as mutations that accumulate in the introns are not under any selection pressures and hence are highly unique to individuals.

Just to clarify a little on introns.

Not all DNA that doesn't go on to translation is an intron. Only DNA which is transcribed and then removed in mRNA processing is considered an intron. There are actually vast sections of DNA (by far the majority) between genes that aren't considered introns. We call this DNA non-coding DNA because it doesn't get transcribed.

It's also worth noting as well that an intron in one cell may not be an intron in another. Biology textbooks on the new course do reference alternative splicing (although I'm not convinced this is necessary knowledge for your exams...I think it's overkill by the texts). So in some cases, an intron might be removed in processing, but in others it might not. In these latter cases, it's not an intron...it's an exon. [it does get a bit more complicated than this, but I think we're probably at our limit already].

In short, it's confusing! If you're worried about this area remember that introns are sequences that get in the way and are thus removed in post-transcriptional modification.




I'm also interested to know why you think (@Jem_) that the genetic code is not quite universal?

[Ahmad_A_1999]

Can someone please explain this statement to me, it is said in my textbook,

"When the product of a biochemical reaction increases, it slows down the reaction that forms it causing the reactants to accumulate."

Why is this the case?

[Quantum44]

Can someone please explain this statement to me, it is said in my textbook,

"When the product of a biochemical reaction increases, it slows down the reaction that forms it causing the reactants to accumulate."

Why is this the case?

Generally for biochemical reactions, the products will inhibit the reaction so reactants aren't wasted when the products are in excess. Thus, the reactants will accumulate so when the products are needed, the reaction can occur.

[omgvce]

The absorption spectrum for plants follows a general trend of high absorption for blue (400-450nm) and red (650-700nm) light with low absorption for everything in between. Although for specific pigments it varies slightly. As far as I'm aware, blue light is absorbed more than red light so blue light would be better for photosynthesis.

The absorption spectrum for plants follows a general trend of high absorption for blue (400-450nm) and red (650-700nm) light with low absorption for everything in between. Although for specific pigments it varies slightly. As far as I'm aware, blue light is absorbed more than red light so blue light would be better for photosynthesis.

https://www.khanacademy.org/science/biology/photosynthesis-in-plants/the-light-dependent-reactions-of-photosynthesis/a/light-and-photosynthetic-pigments

This article has a good explanation

Edit:

Actually it seems that while blue light is absorbed better, the energy absorbed is not as efficiently used for photosynthesis as the red light due to carotenoids.

Here is another article explaining this

https://www.researchgate.net/post/Why_the_rate_of_Photosynthesis_is_higher_in_red_light_while_the_rate_of_absorption_is_highest_of_blue_light

https://www.khanacademy.org/science/biology/photosynthesis-in-plants/the-light-dependent-reactions-of-photosynthesis/a/light-and-photosynthetic-pigments

This article has a good explanation

Edit:

Actually it seems that while blue light is absorbed better, the energy absorbed is not as efficiently used for photosynthesis as the red light due to carotenoids.

Here is another article explaining this

https://www.researchgate.net/post/Why_the_rate_of_Photosynthesis_is_higher_in_red_light_while_the_rate_of_absorption_is_highest_of_blue_light

Oh I see. Thanks!

[ImmaculateJeff]

anyone know of a really good methods or them tutor? Need one ASAP

[Apricot]

In regards to doing revision through exam style questions, I've been reading about checkpoints and seen that many people disapprove of it because it uses past VCAA exam questions. Could someone please outline any other alternative resources which provide good exam style questions and can be used for revision?

[Sine]

In regards to doing revision through exam style questions, I've been reading about checkpoints and seen that many people disapprove of it because it uses past VCAA exam questions. Could someone please outline any other alternative resources which provide good exam style questions and can be used for revision?

non-VCAA commercial exams which your school should provide you with - or you can ask around! (although this allowed on AN for copyright issues)

I'd say it's good to do at least a few VCAA exams early just to get a feel of the exams and the types and difficulty of questions VCAA give you.

[Quantum44]

In regards to doing revision through exam style questions, I've been reading about checkpoints and seen that many people disapprove of it because it uses past VCAA exam questions. Could someone please outline any other alternative resources which provide good exam style questions and can be used for revision?

As Sine said, you can use non-VCAA and VCAA exams as revision, however those are more for exam revision. For SAC revision it is good to do exam style questions, but checkpoints does ruin the VCAA exams you will be doing at the end of the year, so I'd recommend using NEAP study questions as they are similar to checkpoints and allow targeted revision using exam style questions but are not just copied and pasted from VCAA exams.

[Sine]

If you can get a hold of a ton of non-VCAA exams (like I was able to) there was no need to "save" exams for the end of the year but just complete all the relevant + topics that you have learnt. (you can always come back later to those exams when you have learnt enough)

[jem_]

I have a couple of questions:
The study design says we must know about "RNA processing" - is this the same as post transcription modification?
Also, the textbook talks about "alternative splicing of pre-mRNA", but I can't find any mention of that in the study design. Do we need to know about it?
Thanks!