VCE Biology Question Thread

[vox nihili]

Thanks

What property of DNA allows it to be separated into different sizes in gel electrophoresis?
Different company papers each have different answers. Engage says mass only, while neap says charge. I asked this question before, but am asking again as I confused to what to write

Mass, not charge.

Physically, the charge allows you to move the DNA molecules. However, the charge is constant (i.e. each DNA molecule has the same charge). The mass of each molecule, however, is dependent upon its size. Therefore, you can separate by mass, but not by charge.




Here's a question for you guys (sorry I haven't been around very much to help out!).

A new mother presents to her paediatrician worried that her son is smaller than other people his age. After some investigation, the doctor determines that the mother is correct, and diagnoses the child as having an issue with his growth. The doctor suspects that the child has an issue with growth hormone and investigates. He discovers that the anterior pituitary is normal and the gene for growth hormone is also normal.

Looking at the pathway provided below, give three different reasons the baby isn't growing properly.

[homosapien]

Possible to get a 40+ with an A for unit 3, A+ for unit 4, ranked top 5 and aiming for A+ on exam??

[solution]

Possible to get a 40+ with an A for unit 3, A+ for unit 4, ranked top 5 and aiming for A+ on exam??

Yes

[Butterflygirl]

I really need help with the following question. I tried to search it up and I can't find an explanation of the proper way to answer it.

Affected female has genotype X^A X^a and she is crossed with unaffected male. What would be the probability of them having a son without this condition? Explain your answer.

I get that the mother's genotype is X^A X^a and father's is X^a Y and when they are crossed out of four options, 50% are unffected. However, if its a "son" they're asking for, wouldn't it be 25%? because 50 % chance of being a boy and 50% chance of being affected multiplied together?

I always get confused with these questions because in some answers they don't worry about the boy and in some, they do.

The answer for this is 50%

Help is highly appreciated

[The Usual Student]

Mass, not charge.

Physically, the charge allows you to move the DNA molecules. However, the charge is constant (i.e. each DNA molecule has the same charge). The mass of each molecule, however, is dependent upon its size. Therefore, you can separate by mass, but not by charge.




Here's a question for you guys (sorry I haven't been around very much to help out!).

A new mother presents to her paediatrician worried that her son is smaller than other people his age. After some investigation, the doctor determines that the mother is correct, and diagnoses the child as having an issue with his growth. The doctor suspects that the child has an issue with growth hormone and investigates. He discovers that the anterior pituitary is normal and the gene for growth hormone is also normal.

Looking at the pathway provided below, give three different reasons the baby isn't growing properly.

(Image removed from quote.)

I really have no clue but gonna give it a shot

1) A problem with the hypothalamus has caused it to reduce the signals sent to the anterior pituitary to instigate the secretion of the growth hormone , causing less growth hormone to be secreted.
2) the child may have low glucose blood levels  due to malnutrition causing the majority of the growth hormone to follow the chemical pathways which results in an increase in blood glucose levels, hence, less growth hormone follows the pathway in which cartilage growth and bone and tissue growth is instigated causing the child to have growth deficiencies
3) idk lol no clue

most of this was BS but i would like to see if i hit some targets
.

 

[lyoko]

I really need help with the following question. I tried to search it up and I can't find an explanation of the proper way to answer it.

Affected female has genotype X^A X^a and she is crossed with unaffected male. What would be the probability of them having a son without this condition? Explain your answer.

I get that the mother's genotype is X^A X^a and father's is X^a Y and when they are crossed out of four options, 50% are unffected. However, if its a "son" they're asking for, wouldn't it be 25%? because 50 % chance of being a boy and 50% chance of being affected multiplied together?

I always get confused with these questions because in some answers they don't worry about the boy and in some, they do.

The answer for this is 50%

Help is highly appreciated

Hi,

I'm not too sure how clear my explanation is but I'll give it a shot.

You are correct in the sense that 50% are unaffected, 1 boy and 1 girl. However I think that because they are only asking for 'sons' that you only look at how many sons they can have. In this case, it's one affected boy and one unaffected boy. The question asks for how many affected sons, so therefore out of the two sons, only one is affected hence 50%.

Hope that helped and sort of made sense to you

[AhNeon]

A new mother presents to her paediatrician worried that her son is smaller than other people his age. After some investigation, the doctor determines that the mother is correct, and diagnoses the child as having an issue with his growth. The doctor suspects that the child has an issue with growth hormone and investigates. He discovers that the anterior pituitary is normal and the gene for growth hormone is also normal.

Looking at the pathway provided below, give three different reasons the baby isn't growing properly.

(Image removed from quote.)

1)The boy has high stress and cortisol levels resulting In the hypothalamus not triggering the release of GH by anterior pituitary gland
2)The boy is malnutrition(ed?) and does not eat enough resulting in the hypothalamus not triggering the release of GH by anterior pituitary gland
3)Receptors on some or most bone and muscle cells responsible for attaching to growth hormone and initiating the 'growth' response are not properly shaped complementory to the growth hormone, thus causing the inability of the 'growth' response
Full guessed but hopefully i hit at least 1 of the marks.

Also, For 2013 question 5)b) A teenager with a family history of an autoimmune disease underwent a genetic screen for the disease. After
receiving a positive result for the genetic screen, she had an additional autoantibody test. The result of this
autoantibody test was negative.
Explain why the autoantibody test could be negative even though the genetic screen was positive

The answer seems really vague for me. My answer was something got to do with the antigens on the tissue cells which is affected by the particular autoimmune disease being misshaped and likely to be read as non-self, however the specific lymphocytes that are responsible for this have not yet come into contact with these antigens.
So im probably not correct but even so, if someone is screened as having an autoimmune disease, what does that mean? Do they have misshapen antigens on self-cells or is that not even how it works

[solution]

When designing an experiment, is it necessary to explicitly state the control group, (in)dependent variables, supporting results. What I mean by this is stating it , then writing (Dependent Variable) or something like that.

[Angelx001]

Are endocytosis & exocytosis a form of active transport?
Explain how a monosaccharide enters an epithelial cell:
"Monosaccharides moves by facilitated diffusion or active transport. This occurs via protein channels or by protein carrier molecules."

When monosaccharides enter an epithelial cell, it is in the same way for any type of cell in the body?

[hodang]

Hi,

I'm not too sure how clear my explanation is but I'll give it a shot.

You are correct in the sense that 50% are unaffected, 1 boy and 1 girl. However I think that because they are only asking for 'sons' that you only look at how many sons they can have. In this case, it's one affected boy and one unaffected boy. The question asks for how many affected sons, so therefore out of the two sons, only one is affected hence 50%.

Hope that helped and sort of made sense to you

I'm pretty sure that it is 25% because there's a 1/2 chance of receiving a boy, and a 1/2 chance of it being unaffected, so 1/2 X 1/2 = 1/4 (25%) This is only if it's an X-linked trait,

However I'm pretty sure if it were too be Autosomal, it would be a 50% chance

Can someone please confirm this? Because I've done similar questions and this is how they've done it. Thanks

[Angelx001]

The lack of nucleic acid in virsues, the host cell cannot be programmed to replicate viruses. But how does the infection spread then? I thought viruses could infiltrate cells & cause cells with viruses to proliferate?

[Angelx001]

Is testosterone a hormone that is transported through the blood to one or more types of cells?

[sweetcheeks]

The lack of nucleic acid in virsues, the host cell cannot be programmed to replicate viruses. But how does the infection spread then? I thought viruses could infiltrate cells & cause cells with viruses to proliferate?

Could you please elaborate further. I would be reluctant to call a virus without nucleic acid a virus, as it would just be a protein shell.

[The Usual Student]

The lack of nucleic acid in virsues, the host cell cannot be programmed to replicate viruses. But how does the infection spread then? I thought viruses could infiltrate cells & cause cells with viruses to proliferate?

isn't it a lack of a nucleus not Nucliec acid? Viruses can have DNA or RNA

[Angelx001]

isn't it a lack of a nucleus not Nucliec acid? Viruses can have DNA or RNA

Could you please elaborate further. I would be reluctant to call a virus without nucleic acid a virus, as it would just be a protein shell.

I copied the answer off VCAA