HSC Biology Question Thread

[angelahchan]

Hi, could someone please help explain rhodopsin being sensitive to blue-green light? I'm confused because aren't rods responsible for black and white vision?

[sidzeman]

Stupid question but, in humans the diploid number is 46 therefore every cells has 23 pairs of homologous chromosomes. However in males the X and Y chromosomes are not homologous, so do we still say that they have 23 pairs?

[angelahchan]

Stupid question but, in humans the diploid number is 46 therefore every cells has 23 pairs of homologous chromosomes. However in males the X and Y chromosomes are not homologous, so do we still say that they have 23 pairs?

You can still say that males have 23 pairs. Just that   22 pairs (of autosomes) are homologous  and 1 pair (of sex chromosomes) isn't. In general if you say something like "humans have 23 pairs of chromosomes" it'll be fine.

[juliamillburn]

Can Anyone do a quick summary of how to answer ethics questions in the biotechnology option?
I don't know how to squeeze 4-6 marks out of ethics

[sidzeman]

You can still say that males have 23 pairs. Just that   22 pairs (of autosomes) are homologous  and 1 pair (of sex chromosomes) isn't. In general if you say something like "humans have 23 pairs of chromosomes" it'll be fine.

Alright thanks for clarifying haha
For gene therapy in genetics could someone also explain the difference between ex vivo and invo gene therapy. Also, for producing linkage maps, the dihybrid cross must be between 2 homozygous recessive and double heterozygous correct?

[bimberfairy]

Alright thanks for clarifying haha
For gene therapy in genetics could someone also explain the difference between ex vivo and invo gene therapy. Also, for producing linkage maps, the dihybrid cross must be between 2 homozygous recessive and double heterozygous correct?

Hi! I'm not too sure about your second question, but I can definitely answer your question on ex vivo and in vivo gene therapy.

In vivo gene therapy is the DIRECT delivery of genes into cells in the body, and are usually carried out by viral or non-viral vectors like injections, biolistic gene guns etc.

On the other hand, ex vivo gene therapy is INDIRECT. The genes you want to administer aren't directly "inserted" into the body. Instead, the defective cells of the patient are often taken out, grown in a culture, and within that culture, the genes are added. This whole "bundle" (in simpler terms) is then grown and transplanted back into the patient.

Hopefully that cleared things up!

[archie33]

Hey,
I'm just a bit confused about Sutton & Boveri's contributions, like what did they establish at the end of the day?
I can't seem to figure out what they did, and if they both found out the same thing about chromosomes.

[sophiegmaher]

Hey,
I'm just a bit confused about Sutton & Boveri's contributions, like what did they establish at the end of the day?
I can't seem to figure out what they did, and if they both found out the same thing about chromosomes.

They together determined that Chromosome Theory of Inheritance: that patterns of inheritance in mammals matched those established by Mendel and his pea plants. So, they found that the law of random segregation, the law of independent assortment, and the law of simple dominance applied in mammals by testing sea urchin eggs, in relation to Boveri, and grasshopper testes, in Sutton's case. It is important to note that each of them were observing the process of meiosis in each of these two different organisms, hence the fact that these same laws applied to them enhances the reliability of the theory. This theory also includes that chromosomes are found in the nucleus, where previously it was thought to be found in the cytoplasm AND the nucleus, and that fertilisation allows new pairs of chromosomes to form as those that randomly segregate/independently assort come together.

And to answer the latter part of your question, they found out slightly different things that all contributed to the one theory explained above!
There are heaps of youtube videos on them if you need further clarification.
Hope that makes sense

[sophiegmaher]

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

And also diffusion and osmosis can only move along the concentration gradient, whereas some nutrients need to be moved against it: hence the need for active transport. This is seen through uric acid, where it needs to move against the concentration gradient from blood into the urine in the kidney at the proximal convoluted tubule. Also, if osmosis was only used, too much water would be lost in urine as the high concentration of wastes would create a concentration gradient that would lead to water being drawn in by osmosis, leading to an inability to conserve water in organisms that may inhabit arid areas, such as the spinifex hopping mouse.

[c.conol]

Hello! Would they ever ask us to design an epidemiological study?

[sophiegmaher]

Hello! Would they ever ask us to design an epidemiological study?

There was an 8 marker asked in a HSC paper, I can't remember when but it was a fairly older paper I think. It gave a scenario and you had to discuss how an epidemiological study could be used to find the cause of the infections disease. So I guess the general answer to your question is: yes they can, unfortunately :/

[c.conol]

There was an 8 marker asked in a HSC paper, I can't remember when but it was a fairly older paper I think. It gave a scenario and you had to discuss how an epidemiological study could be used to find the cause of the infections disease. So I guess the general answer to your question is: yes they can, unfortunately :/

How would I go about answering this question? I'm stumped.

[angelahchan]

There was an 8 marker asked in a HSC paper, I can't remember when but it was a fairly older paper I think. It gave a scenario and you had to discuss how an epidemiological study could be used to find the cause of the infections disease. So I guess the general answer to your question is: yes they can, unfortunately :/

it was in the 2004 paper

[sophiegmaher]

How would I go about answering this question? I'm stumped.

I'm no expert, but I would break the question down in correspondence to the 4 marks that are allocated to it. In general, I would focus on the main features that you know are a part of an epidemiological study and just link it to the scenario given by the question:
1. Create a large population sample of individuals with diverse backgrounds, including living in different areas, differences in age and gender, occupation, lifestyle, etc
2. Gather data on the eating habits of those affected and those not affected, paying particularly attention to if fish is the main food source or meat, due to the recent chemical factor that had started up nearby.
3. Gather data on the location the individuals affected and not affected live: i.e if they live near the far side of the bay where the chemical factory is situated
4. Compare the data gathered on the affected and control groups and interpret for trends: i.e: similarities, differences. You could also potentially make a prediction as to what the cause of the symptoms may be, which, judging from the information provided, you could hypothesise that it is the chemical run-off from the chemical factory into the water that the fish, which is the main food source for town, live. Thus, individuals who eat a diet mainly of fish have contracted the disease.

What HSC paper is it from?

[c.conol]

I'm no expert, but I would break the question down in correspondence to the 4 marks that are allocated to it. In general, I would focus on the main features that you know are a part of an epidemiological study and just link it to the scenario given by the question:
1. Create a large population sample of individuals with diverse backgrounds, including living in different areas, differences in age and gender, occupation, lifestyle, etc
2. Gather data on the eating habits of those affected and those not affected, paying particularly attention to if fish is the main food source or meat, due to the recent chemical factor that had started up nearby.
3. Gather data on the location the individuals affected and not affected live: i.e if they live near the far side of the bay where the chemical factory is situated
4. Compare the data gathered on the affected and control groups and interpret for trends: i.e: similarities, differences. You could also potentially make a prediction as to what the cause of the symptoms may be, which, judging from the information provided, you could hypothesise that it is the chemical run-off from the chemical factory into the water that the fish, which is the main food source for town, live. Thus, individuals who eat a diet mainly of fish have contracted the disease.

What HSC paper is it from?

This is from a trial paper I found online