HSC Biology Question Thread

[phebsh]

Hi there, anything in particular we are recommended to do today being the day before the bio exam?

[angelahchan]

Also, what's the difference between photopsin and iodopsin? The text book says one and some youtube videos say the other, but I think they're pretty much the same as they're both describing the photosensitive pigment in cone cells?

i think you can use the two terms interchangeably, since I've tried to look for differences and most sources do the same. This definition of photopsin does talk about their differences: "The protein component of the pigment iodopsin in the cones of the retina of the eye." So I'm guessing photopsin is a component of iodopsin?

[adelaidecruz]

Considering the difficulties of the exams this year, I think it's better to know about both kinds: perfluorocarbons, and haemoglobin-based oxygen carriers.
I would also recommend outlining the disadvantages and advantages for each.

Awesome, thank you!

[adelaidecruz]

Hi there, anything in particular we are recommended to do today being the day before the bio exam?

Maybe read over your notes and work on your weak points? I personally saved all the multiple choice from 2016-2004 for a chill study sesh today lol

[phebsh]

Maybe read over your notes and work on your weak points? I personally saved all the multiple choice from 2016-2004 for a chill study sesh today lol

Great idea, thanks!!

[angelahchan]

Hey, I've been going through some past papers and i'm so stuck on what is actually required for this question (method? variables? equipment?), any ideas would be greatly appreciated!
"Plant breeders have developed a new variety  of terrestrial plant which has one structure   
that   appears to assist in water conservation in hot, dry environments.
Design a first-hand   investigation the plant breeder could use to determine of this structure   
assists in   water conservation." (4 Marks)

   

So the marking guidelines for this question are really brief:
Better responses outlined the features of good experimental design, including aspects such as
control of variables, repetition and data collection.

Here's an exemplar response from the success one hsc bio
1) Take a reasonable quantity of each of the new variety possessing the special feature and a similar species that does not possess the new feature
2) Plant the individual plant specimens in identical conditions (pot type and size, soil type and quantity)
3) Place half each type of the specimens in the same hot, dry environment and the other half in the same relatively hot, moist enivronment
4) Water specimens sparingly over the period (e.g. once per 2 week cycle) with an identical measured amount of water
5) Monitor each group over a period of time, measuring growth, new leaf production/loss of leaves, and recording results in a table of chart

So I'll try to break down the marks for you
1) Clear method, easy to follow through - i.e. the steps are in order from one another- when followed your method must clearly test out the aim
2) State what variables you would control and how you'd do it, as well as which one you would change
3)  State how you would repeat the experiment for reliability - e.g. in the exemplar with the "reasonable quantity of each variety" of plants -  you could state how many plants as well for specificity
4) State how you would record the data and what would you be recording, as well as how long you would be recording it for- e.g. the exemplar writes about measuring growth and recording it in a chart.

[adelaidecruz]

Hi can anyone please help me with this dot point in MAB "inadequacy of diffusion and osmosis in waste removal". Here's an outline of my notes on it. Just wanna know if these are enough of if there are any errors. Thanks
- Not fast enough to maintain required solute concentration in the cell and to remove significant buildup of nitrogenous wastes
- Slows down once the difference in concentration gradient becomes smaller and stops once concentrations have hit equilibrium
- Diffusion: toxins can only be removed if there was a high concentration of it in the blood than in the urine itself.
- Osmosis: would only remove toxins if it is dissolved in water; if there is a high concentration of urine, water will continually be drawn out from the body to even out the concentration gradient.

[phebsh]

Hi can anyone please help me with this dot point in MAB "inadequacy of diffusion and osmosis in waste removal". Here's an outline of my notes on it. Just wanna know if these are enough of if there are any errors. Thanks
- Not fast enough to maintain required solute concentration in the cell and to remove significant buildup of nitrogenous wastes
- Slows down once the difference in concentration gradient becomes smaller and stops once concentrations have hit equilibrium
- Diffusion: toxins can only be removed if there was a high concentration of it in the blood than in the urine itself.
- Osmosis: would only remove toxins if it is dissolved in water; if there is a high concentration of urine, water will continually be drawn out from the body to even out the concentration gradient.

Yeah I think the main idea is that they are slow and passive processes and it's inadequate for larger organisms because they build up toxins quickly and therefore need more efficient processes to remove waste

[liya1234]

I've got so many last minute q's sorry! Would someone be able to help me with this dot point in the genetics option: "explain how the use of recombinant DNA technology can identify the position of a gene on a chromosome" - is it okay just to talk about the FSH method here? Also what would come under "identify the role of genes in embryonic development", I'm really lost with this one and can't really find anything online. Thank you so much!

[Opengangs]

I've got so many last minute q's sorry! Would someone be able to help me with this dot point in the genetics option: "explain how the use of recombinant DNA technology can identify the position of a gene on a chromosome" - is it okay just to talk about the FSH method here? Also what would come under "identify the role of genes in embryonic development", I'm really lost with this one and can't really find anything online. Thank you so much!

Yeahh, but you need to go in great detail about the process of "Fluorescent In Situ Hybridisation".

Talk about probes as a sequence of DNA that has been prepared through the process of recombinant DNA technology.
Talk about how the probe is annealed so that the DNA denatures.
Talk about the binding of the probe to the actual gene (by complementary base pairing).
Talk about how the probes are then placed under electrophoresis gel, where the probes can then be used to identify the locus of the gene along a chromosome.

Role of genes:
We have two main genes that compose of embryonic development:
The first one is called a structural gene, and these encode for polypeptides that code for the proteins and enzymes of the embryo.
The second one is called a regulatory gene, and these control the expression of the structural genes.

We also have a third gene, a homeotic gene that encodes for the patterns of development within the early stages of embryonic development.

[biancakhalil0106]

For HSC bio exam do we draw in pencil or pen? because it says to only use black pen.

[angelahchan]

For HSC bio exam do we draw in pencil or pen? because it says to only use black pen.

Pen. If you're unsure, do it in pencil first then trace over with pen. this is because the papers are scanned (I think  markers were given physical copies in the past), and pencil wouldn't be able to show well

[sidzeman]

Follow up to the "how can recombinant DNA be used to identify the position of a gene on a chromosome" question -
1)   The protein that is produced by that gene is used to determine the amino acid sequence  this is used to synthesise a DNA sequence (probe) that would be complementary to the gene of interest
2)   Using heat DNA strands are denatured – split into single strands (similar to DNA hybridisation)
3)   Fluorescent probes – synthetic strands of DNA that are complementary to the gene wishing to be located, produced in step 1
4)   Probes are added to the slide of the denatured DNA strands
5)   As DNA and probe are both single stranded – they will bind together where the bases are complementary
6)   The area at which they are joined will glow due to the fluorescence of the probe – therefore position of gene on chromosome is determined

Would this be a sufficient amount of detail? I'm not too sure about the last step

[liya1234]

Yeahh, but you need to go in great detail about the process of "Fluorescent In Situ Hybridisation".

Talk about probes as a sequence of DNA that has been prepared through the process of recombinant DNA technology.
Talk about how the probe is annealed so that the DNA denatures.
Talk about the binding of the probe to the actual gene (by complementary base pairing).
Talk about how the probes are then placed under electrophoresis gel, where the probes can then be used to identify the locus of the gene along a chromosome.

Role of genes:
We have two main genes that compose of embryonic development:
The first one is called a structural gene, and these encode for polypeptides that code for the proteins and enzymes of the embryo.
The second one is called a regulatory gene, and these control the expression of the structural genes.

We also have a third gene, a homeotic gene that encodes for the patterns of development within the early stages of embryonic development.

Okay thank you so much!!! Just about the electrophoresis gel - why is that used here? I thought fluorescence microscopes were used to identify the position of the probe on the chromosome?

[Opengangs]

Okay thank you so much!!! Just about the electrophoresis gel - why is that used here? I thought fluorescence microscopes were used to identify the position of the probe on the chromosome?

Ahah, my mistake. Gel electrophoresis is used in DNA fingerprinting.
You use the fluorescence microscopes to identify loci.