VCE Biology Question Thread

[Gogo14]

Some more qs,

http://imgur.com/i74Cf4z
For q16.
Are we expected to know that thyroxine is hydrophobic, even though it is an amino acid derivative?
If this comes up in the exam, what do we write
http://imgur.com/u8vZrkb

Q9
Why is C not correct? Doesn't non competitive inhibitors alter the tertiary structure of enzymes?
http://imgur.com/z03kA0u
I really don't get why the diagram is cell signalling/signal transduction for 5b. I wrote paracrine (signalling)

[geminii]

Do we need to know about things like gap junctions + plasmodesmata in how cells communicate with each other?
What about paracrine and autocrine signalling?

[FatimaEl]

Can anyone tell me a simple way of calculating half life related questions such as this one?

The half-life of carbon 14 is 5730 years. A sample of well-preserved woolly mammoth
(Mammuthus primigenius) was used to determine its absolute age. If the mammoth lived in the
present the sample would have contained 1g of C14; however, the sample only contained 0.03g of
C14. This would mean the woolly mammoth was approximately
A. 11500 years old
B. 17000 years old
C. 23000 years old
D. 28500 years old

I seem to always get these wrong, and since were not allowed calculators, a simple way to get the answer would be  much appreciated! 

[cosecant]

Can anyone tell me a simple way of calculating half life related questions such as this one?

The half-life of carbon 14 is 5730 years. A sample of well-preserved woolly mammoth
(Mammuthus primigenius) was used to determine its absolute age. If the mammoth lived in the
present the sample would have contained 1g of C14; however, the sample only contained 0.03g of
C14. This would mean the woolly mammoth was approximately
A. 11500 years old
B. 17000 years old
C. 23000 years old
D. 28500 years old

I seem to always get these wrong, and since were not allowed calculators, a simple way to get the answer would be  much appreciated! 

Personally, I figure out how many half lives have elapsed. So in this case the original sample was 1g, after one half life it would be 0.5g and then after another it would be 0.25, 0.125, 0.0675, 0.03125 so therefore five half lives has elapsed and since the half life of carbon 14 is 5730 years, 5730 x 5 is definitely over 25000 (since 5 x 5000=25000), which would give D.

However, I doubt VCAA would actually ask this specific question as finding the number of half lives in this case is a bit tedious and time consuming, they would probably go for max 3 half lives not 5.

[FatimaEl]

Personally, I figure out how many half lives have elapsed. So in this case the original sample was 1g, after one half life it would be 0.5g and then after another it would be 0.25, 0.125, 0.0675, 0.03125 so therefore five half lives has elapsed and since the half life of carbon 14 is 5730 years, 5730 x 5 is definitely over 25000 (since 5 x 5000=25000), which would give D.

However, I doubt VCAA would actually ask this specific question as finding the number of half lives in this case is a bit tedious and time consuming, they would probably go for max 3 half lives not 5.

thank you for the reply! and yes i highly doubt they'd make us spend too much time on a one mark mc, but who knows

[Rob16]

im kinda confused when interphase occurs before meiosis, a human chromosome will be 2n (or 4n?) with 46 double stranded chromosomes and then after meiosis I become 2n (but it was 2n before or...?) with 23 double stranded chromsomes in each of the 2 cells. Then after meiosis II become n with 23 single stranded chromosomes in each of the 4 gametes?

is this right?

[Vaike]

Hey everyone,

Just wondering if anyone would be able to lend a hand with this question? I don't understand why A is wrong, as far as I know leucocytes that kill virus infected cells (Cyto toxic T lymphocytes) mature in the thymus and this would also be deficient like T helper cells from option A? The answer VCAA gave was B. Thanks

[vox nihili]

im kinda confused when interphase occurs before meiosis, a human chromosome will be 2n (or 4n?) with 46 double stranded chromosomes and then after meiosis I become 2n (but it was 2n before or...?) with 23 double stranded chromsomes in each of the 2 cells. Then after meiosis II become n with 23 single stranded chromosomes in each of the 4 gametes?

is this right?

It's almost correct, but you've just got to be careful about the words you use


Before replication, each chromosome has one molecule of DNA, which is made up of two strands. After replication, each chromosome is duplicated, such that it contains two molecules of DNA. These are now called chromatids.

So before meiosis I, the cell is 2n but each chromosome has two chromatids. After meiosis I the daughter cells are n and each chromosome has two chromatids. AFter meiosis II the cells stay n, and each chromosome has one chromatid.

Hey everyone,

Just wondering if anyone would be able to lend a hand with this question? I don't understand why A is wrong, as far as I know leucocytes that kill virus infected cells (Cyto toxic T lymphocytes) mature in the thymus and this would also be deficient like T helper cells from option A? The answer VCAA gave was B. Thanks

Absolute shocker of a question to be honest.
A is wrong because of NK cells.

[Angelx001]

Suggest one possible situation which could result in an increase in the number of cases of mumps occurring. Justify your response (2 marks)
Answer: "The mumps will develop resistance against the vaccine through a mutation.
Hence, people will become infected again"
Is this answer correct to gain 2 marks?

[AhNeon]

If an individual has a translocated chromosome (let's say 21 and 23 just join together for 1 set so there are chromosome 21, 23 and translocated (21/23)), would the translocated chromosome undergo crossing over with a homologous pair. What would be its homologous pair if it did. Or does it act like a y chromosome and just mind its own business?

[vox nihili]

Suggest one possible situation which could result in an increase in the number of cases of mumps occurring. Justify your response (2 marks)
Answer: "The mumps will develop resistance against the vaccine through a mutation.
Hence, people will become infected again"
Is this answer correct to gain 2 marks?

I'd only give it one mark. You don't make any reference to the question in your answer. The question specifically asks you to talk about how the number of cases could increase—you needed to explain the link.

"A mutation in the mumps virus makes the virus resistant to the mumps vaccine. The resistant virus is thus able to infect people vaccinated against the virus, leading to an increase in the number of mumps cases".

Another option would be to talk about a drop in the vaccination rate, which I'm pretty sure is what's happened recently

Anyway tl;dr right thinking but need to be clearer

If an individual has a translocated chromosome (let's say 21 and 23 just join together for 1 set so there are chromosome 21, 23 and translocated (21/23)), would the translocated chromosome undergo crossing over with a homologous pair. What would be its homologous pair if it did. Or does it act like a y chromosome and just mind its own business?

The answer is well beyond VCE, so you definitely don't need to know.

Simply though, it could actually line up with either one. Translocations like this are a big source of chromosomal abnormalities in foetuses.

Just for fun, and once again well beyond VCE, the Y chromosome actually lines up with the X...otherwise how do we ensure that each gamete only gets one X or one Y?

[Steph.Y]

Hello!
Could someone please give me an example of when to use VSRIG (the sequence of events that occur in natural selection)?

[Angelx001]

What does VSRIG stand for?

[The Usual Student]

Hello!
Could someone please give me an example of when to use VSRIG (the sequence of events that occur in natural selection)?

Do u mean like
- Variation
- Selection features
ect?

[Gogo14]

1. Why can there be only 2 forms of a gene in any one cell?
2. How can you exhibit genetic characteristics that neither your mother nor father show?
Was thinking recessive traits but the word genetics threw me off. Mutations?
3. In snapdragons, red allele flower colour(R) and white flower colour (R') combine to prodyce pink flowers (RR'). Why do you have to use these kinds of letters shown?
4. Red cattle(RR) white cattle(WW) produces both red and white coloured cattle (RW). Why do you have to use the kinds of letters shown?