Psyxwar's Biology 3/4 Question Thread

[Yacoubb]

K so, when would you find a single stranded chromosome apart from say, Anaphase and Telophase in mitosis (and I guess Anaphase II and Telophase II in meiosis)? Since they're usually depicted as such, but I can't really think of any other circumstance where they would be single stranded.

You would only find single-stranded chromsomes during the G1 phase of interphase, Anaphase and Telophase. The other stages would have double-stranded chromsomes because the genetic material duplicates.

[psyxwar]

You would only find single-stranded chromsomes during the G1 phase of interphase, Anaphase and Telophase. The other stages would have double-stranded chromsomes because the genetic material duplicates.

Fair enough, thanks.

[Yacoubb]

Ah I see. But are they present in interphase considering that it's just present as chromatin then?

Valid point! I guess if you considered them joining up in Metaphase then its only Anaphase and Telophase. Because really, interphase is the coiling and condensing of the genetic material!

[psyxwar]

Valid point! I guess if you considered them joining up in Metaphase then its only Anaphase and Telophase. Because really, interphase is the coiling and condensing of the genetic material!

lol nah dw, changed my post. Think they're still considered chromosomes in all phases of cell cycle, just are only visible as single stranded chromosomes during Anaphase and Telophase, but otherwise during G1 they are still single stranded chromosomes.

[psyxwar]

Okay, so VCAA says to treat someone who has measles, you need to vaccinate them. Does this work?

[vox nihili]

Okay, so VCAA says to treat someone who has measles, you need to vaccinate them. Does this work?

It can do. I'm not sure about measles specifically, but there are diseases that will react to vaccination before symptoms appear. Rabies is an example of that. If symptoms show up, it's a death sentence, but if you're vaccinated before symptoms come about, then you'll almost certainly survive the disease.

[Russ]

You can give someone exposed to measles the vaccine and it can still be effective. You can't treat measles with vaccination (there isn't actually a treatment)

[psyxwar]

Okay thanks.

Would it be more accurate to say that antibodies are specific to certain epitopes rather than certain antigens? I've read that different antibodies can be specific to different epitopes on the same antigen.

[vox nihili]

Okay thanks.

Would it be more accurate to say that antibodies are specific to certain epitopes rather than certain antigens? I've read that different antibodies can be specific to different epitopes on the same antigen.

Not really. An epitote in itself is an antigen. An antigen is anything that causes an immunogenic response. So antibodies themselves are actually respond to the epitote essentially. Irrespective of whether or not what you're saying is true, I personally don't think it would make any difference in terms of "correctness".

[psyxwar]

Fair enough, thanks.

Regarding binary fission; how much do we need to know?

Would:

• DNA is replicated
• Chromosomes attach to membrane at an attachment point
• Cell elongates/ increases in size, chromosomes move apart
• cleavage furrow forms and cell is split in two

be sufficient?

[vox nihili]

Fair enough, thanks.

Regarding binary fission; how much do we need to know?

Would:

• DNA is replicated
• Chromosomes attach to membrane at an attachment point
• Cell elongates/ increases in size, chromosomes move apart
• cleavage furrow forms and cell is split in two

be sufficient?

Yeah. I certainly didn't know that much detail last year and I managed!

[Russ]

Not really. An epitote in itself is an antigen. An antigen is anything that causes an immunogenic response. So antibodies themselves are actually respond to the epitote essentially. Irrespective of whether or not what you're saying is true, I personally don't think it would make any difference in terms of "correctness".

This isn't strictly true (ie epitope =/= antigen) but the difference is irrelevant at VCE.

[vox nihili]

This isn't strictly true (ie epitope =/= antigen) but the difference is irrelevant at VCE.

Epitote is the portion of the antigen expressed on cells that initiates the immunogenic response. Antigen is anything that initiates an immunogenic response. Is this correct?

Antigen can be a little annoying to define. I've had a look at a few sources previously and they all have slightly different ways of defining exactly what it is.

[Yacoubb]

Fair enough, thanks.

Regarding binary fission; how much do we need to know?

Would:

• DNA is replicated
• Chromosomes attach to membrane at an attachment point
• Cell elongates/ increases in size, chromosomes move apart
• cleavage furrow forms and cell is split in two

be sufficient?

Probably being way to meticulous but...

- Mention the single circular chromosome to create the impression (for assessors) that you understand binary fission is a mode of cell replication in prokaryotic organisms.
- The expansion of the plasma membrane allows for the single circular chromosomes to be separated; the cleavage furrow forms and the cell splits into two identical cells.

That would be sufficient though

Quick Question:
Could I mentioned that a difference between a prokaryotic chromosome and a plasmid is that a plasmid is capable of autonomously replicating, whilst a prokaryotic chromosome requires a signal in order to replicate for binary fission?

[vox nihili]

Probably being way to meticulous but...

- Mention the single circular chromosome to create the impression (for assessors) that you understand binary fission is a mode of cell replication in prokaryotic organisms.
- The expansion of the plasma membrane allows for the single circular chromosomes to be separated; the cleavage furrow forms and the cell splits into two identical cells.

That would be sufficient though

Quick Question:
Could I mentioned that a difference between a prokaryotic chromosome and a plasmid is that a plasmid is capable of autonomously replicating, whilst a prokaryotic chromosome requires a signal in order to replicate for binary fission?

It's good to know more detail, at times. That probably is too much. That cleavage is made by a protein called FtsZ, which constricts it. In animal cells, it's actin I believe. Something you'll encounter in Uni biol as a key difference, though not relevant to this.

As for your quick question. Short answer is no. I know this is at conflict with my previous statement about the FtsZ, but sometimes knowing too much is not a good thing. The exams are marked in relevance to the course. For example, if you use a method in Specialist maths, that you've learned externally...perhaps it's something in Uni, you may very well get a mark for the right answer, though, the marking scheme does not provide for anything that is not part of the prescribed course. Often, extra information can be beneficial in the multiple choice questions (particularly as the difficulty of the science gets greater and things become less "up for interpretation"), however, in short answer questions, you will not be rewarded for giving an answer that is outside of the course. Biology in particular. The marking schemes look for very specific statements, very specific pieces of information. You are guaranteed that these pieces of information are part of the course; it will not suffice to look for them in your extra knowledge!

Having said that though, it is important to have a genuine interest, but, if you can't learn to switch between the two; that is, learn the course and learn what isn't in it, then you're best to stop yourself going too far out of bounds!