Yacoubb's Bio 3+4 Questions

[alondouek]

Short tandem repeats (STRs) are very short pieces of DNA - like, ridiculously short, ~2-6 bp in length. You may have seen them mentioned as microsatellites when studying PCR or DNA fingerprinting. Basically, we can use these STRs for many, many forms of DNA amplification for multitude purposes. In PCR, the microsatellite/STR is what allows for the extension of existing nucleotide sequences.

[vox nihili]

Short tandem repeats (STRs) are very short pieces of DNA - like, ridiculously short, ~2-6 bp in length. You may have seen them mentioned as microsatellites when studying PCR or DNA fingerprinting. Basically, we can use these STRs for many, many forms of DNA amplification for multitude purposes. In PCR, the microsatellite/STR is what allows for the extension of existing nucleotide sequences.

They're also extremely helpful in forensics, because regions with heaps of STRs tend to be "junk" and thus are highly mutable.

[Yacoubb]

Do we need to know about the child from Tuang and Lucy the hominin (the fossils)?

[Scooby]

Do we need to know about the child from Tuang and Lucy the hominin (the fossils)?

nope

[Yacoubb]

nope

Okay thanks (:

[Yacoubb]

Sea anemones produce an organic compound called anthopleurine. When eaten by sea slugs, the chemical is released from the sea slug, warning the other anemones that a predator is approaching. Anthopleurine would best be described as a:
(A) Hormone
(B) Pheromone
(C) Trigger Substance
(D) Neurotransmitter

The given answer is B; but pheromones are signalling molecules that act exclusively on members of the same species from which a particular organism released it. So, how could a signalling molecule released by a sea slug and acting upon other anemones be a pheromone? The only explanation I could think of is that the anemone actually releases the anthopleurine as it is being consumed by the sea slug, which acts on other anemones. I chose C by the way

Could someone please explain? Thanks

[alondouek]

Anthopleurin is definitely a toxin but it also functions as a pheromone; it's used by anemones to retract their tentacles when a predator is detected. When a predator consumes the anemone, areas of the anemone exposed to the environment contain larger-than-usual amounts of anthopleurin, which is then dispersed to the environment so as to warn other anemones.

As a flowchart summary, the action is anemone --> other anemones (as required by pheromones), where the predator acts as a vehicle for the dispersion of the pheromone.

[Yacoubb]

Anthopleurin is definitely a toxin but it also functions as a pheromone; it's used by anemones to retract their tentacles when a predator is detected. When a predator consumes the anemone, areas of the anemone exposed to the environment contain larger-than-usual amounts of anthopleurin, which is then dispersed to the environment so as to warn other anemones.

As a flowchart summary, the action is anemone --> other anemones (as required by pheromones), where the predator acts as a vehicle for the dispersion of the pheromone.

Okay yeah I get it Thanks alondouek

[Yacoubb]

Are australopiths and australopithecines the same thing?

[vox nihili]

Are australopiths and australopithecines the same thing?

Presumably

[Yacoubb]

I've completed a unit 3 paper (insight 2010) and I've found that there are many questions where the suggested solutions seem to be different to mine, but I feel mine are still in a way, correct.

For instance, what is acquired immunity?
My answer: Defence against disease that involves the production of antibodies and memory cells in response to a pathogenic agent.

The answer: Defence against pathogenic agents that is mediated by B and T lymphocytes that is specific, has memory and self-non self recognition.

How do I deal with questions like that? How do I know how harsh to be with my marking?

For instance, another question:

What is amylase and what is its relationship with starch?
I answered that: amylase is an enzyme that catalyses the breakdown of starch into glucose sub-units. But I gave myself 1 out of 2 for it because the answer said that starch was its substrate and you needed to indicate that.

I just feel terrible after all these practice exams because a lot of my answers are still right, just not specific enough. Fml I need help Thanks for any advice/suggestions

[psyxwar]

I've completed a unit 3 paper (insight 2010) and I've found that there are many questions where the suggested solutions seem to be different to mine, but I feel mine are still in a way, correct.

For instance, what is acquired immunity?
My answer: Defence against disease that involves the production of antibodies and memory cells in response to a pathogenic agent.

The answer: Defence against pathogenic agents that is mediated by B and T lymphocytes that is specific, has memory and self-non self recognition.

How do I deal with questions like that? How do I know how harsh to be with my marking?

Their answer is better, as acquired immunity involves both the cell-mediated and humoral responses. Your response pretty much centers on the humoral with antibody production; you don't really touch upon the cell-mediated response, and this might be perceived as a lack of understanding.

tbh just give yourself 0 if there's any doubt. You honestly shouldn't care what you score on trials anyway, so long as you're improving.

What is amylase and what is its relationship with starch?
I answered that: amylase is an enzyme that catalyses the breakdown of starch into glucose sub-units. But I gave myself 1 out of 2 for it because the answer said that starch was its substrate and you needed to indicate that.

Well, saying it acts on amylase is basically saying that starch is its substrate. I wouldn't mention glucose because that's not necessarily correct. Just say it catalyses the breakdown of starch (substrate) into simple sugars.

Actually on second thought it is a 2 mark question and it explicitly mentions its relation to starch, so yeah, guess you had to have the bit about substrate there. Should only be worth a mark tbh...

[Yacoubb]

Yeah guess your right. I wont worry too much about how much I score on trial exams; I'd much rather improving. Thanks

[Scooby]

Just for future reference, glucose and maltose are the products of amylase-catalysed starch hydrolysis

And if you say that amylase acts on starch you are implying that it's the substrate, so you're more than likely going to get the marks

[Yacoubb]

Just for future reference, glucose and maltose are the products of amylase-catalysed starch hydrolysis

And if you say that amylase acts on starch you are implying that it's the substrate, so you're more than likely going to get the marks

Scooby I started my first official Biology unit 3 exam and I got 87% (65/75), which for 2010 was an A+ - I did the 2010 unit 3 Biology Insight exam. Trying to be as picky as possible, so I gave myself only 1 mark out of 2 for that. Just to be on the safe side, should I avoid mentioning the product of an enzyme-substrate reaction unless it specifies?

Any tips other than actually documenting errors? And is it true that questions tend to be repeated in exams that have been used before? (i.e. structure wise)