VCE Biology Question Thread

[Reus]

Isn't it in the 5' to 3' direction?

That's for DNA replication as davomac just mentioned. Just think of the opposite when talking about mRNA synthesis. 

[Scooby]

Isn't it in the 5' to 3' direction?

The mRNA molecule itself is synthesised 5' to 3' (just like the two daughter stands in DNA replication) but the template stand of the DNA itself is read 3' to 5'

[Reus]

2012 Exam multiple choice question, I got the answer of 25 ( A ) however it's 75 ( C ).
I thought it'd be 25 as 25 Adenines are complementary to 25 Thymines hence another 25 Guanine and Cytosine each (100 Nucleotides)
64% of the state also answered A haha.

Could someone explain how it's 75?

[davomac]

2012 Exam multiple choice question, I got the answer of 25 ( A ) however it's 75 ( C ).
I thought it'd be 25 as 25 Adenines are complementary to 25 Thymines hence another 25 Guanine and Cytosine each (100 Nucleotides)
64% of the state also answered A haha.

Could someone explain how it's 75?

As it is double helix and 100 nucleotides 'long', there would actually be 200 nucleotides. 200-(25Adenine and 25Thymine) leaves 150 bases. 75 of which will be guanine.

[nerdmmb]

2012 Exam multiple choice question, I got the answer of 25 ( A ) however it's 75 ( C ).
I thought it'd be 25 as 25 Adenines are complementary to 25 Thymines hence another 25 Guanine and Cytosine each (100 Nucleotides)
64% of the state also answered A haha.

Could someone explain how it's 75?

If there are 25 adenine bases in the double stranded DNA molecule, this means that there is a total of 25 adenine in the DNA strands meaning that there would have to 25 thymine bases to bind to the 25 adenine bases. This leaves us with 75 bases. So there must be 75 guanine bases and 75 cytosine bases that bind to eachother.
Hence there is a total of 75 guanine bases in the DNA molecule.

I hope that makes sense

[Reus]

As it is double helix and 100 nucleotides 'long', there would actually be 200 nucleotides. 200-(25Adenine and 25Thymine) leaves 150 bases. 75 of which will be guanine.

If there are 25 adenine bases in the double stranded DNA molecule, this means that there is a total of 25 adenine in the DNA strands meaning that there would have to 25 thymine bases to bind to the 25 adenine bases. This leaves us with 75 bases. So there must be 75 guanine bases and 75 cytosine bases that bind to eachother.
Hence there is a total of 75 guanine bases in the DNA molecule.

I hope that makes sense

Thanks guys! Didn't read the question correctly, missed out on the 100 nucleotides meant 200 in a double stranded! Appreciate the clarification

[Jason12]

how do linked genes work?

[Reus]

The answer is C.
But are B and D also examples of adaptations/homeostasis?! Could someone explain how it is specifically only C :/ Thanks.

[MM1]

-What are the reasons for DNA amplification when using PCR?

-What are multiple alleles?

Thanks.

[dankfrank420]

@Jason12?

What do you mean by "work"? They lie on the same chromosome ("linked" on the same chromosome) if that's what you're asking.

@Reus

I'm confident in saying that B is not an example of homeostasis. In this case, homeostasis would be the body producing its own sweat in response to heat. However, the situation in option B is that the pool provides the water on the skin - your body is not producing its own sweat.

As for D, I'm unsure. Maybe because there is no signal pathway (receptors, effectors etc) and the changing of the skin is a passive process that doesn't involve a control centre?

@MM1

We use PCR to amplify DNA to:

- amplify small amounts of fossil DNA
- make copies of genes for insertion into other cells
- forensic testing

A multiple allele system is when there are more than two possible alleles. The human ABO blood system is an example of this.

[nhmn0301]

The answer is C.
But are B and D also examples of adaptations/homeostasis?! Could someone explain how it is specifically only C :/ Thanks.

Just a bit add up to what dankfrank has said, D is not an example of homeostasis because that's a behavioral adaptation (think it's in y10 science or something).

[Reus]

@Reus

I'm confident in saying that B is not an example of homeostasis. In this case, homeostasis would be the body producing its own sweat in response to heat. However, the situation in option B is that the pool provides the water on the skin - your body is not producing its own sweat.

As for D, I'm unsure. Maybe because there is no signal pathway (receptors, effectors etc) and the changing of the skin is a passive process that doesn't involve a control centre?

Ah thanks with B Yeah D got me confused haha.

Just a bit add up to what dankfrank has said, D is not an example of homeostasis because that's a behavioral adaptation (think it's in y10 science or something).

Are adaptations not a part of regulating homeostasis? That's what I remember from Unit ½. 

[dankfrank420]

Not really a specific question here, but how do you guys go about determining the mode of inheritance from pedigree charts and/or other sources?

And what justifications do you use? (eg. This trait is autosomal dominant because...)

[nhmn0301]

Ah thanks with B Yeah D got me confused haha.
Are adaptations not a part of regulating homeostasis? That's what I remember from Unit ½. 

The definition of homeostasis is the maintenance of a relatively constant INTERNAL environment blah blah blah, so changing colour to prevent predators probably not homeostasis.

[nerdmmb]

If alcohol is polar, then why does it dissolve in lipids?

Or is it because it contains both polar and non polar regions - amphipathic?