VCE Biology Question Thread

[specimen]

In the 2015 VCAA exam Q9b asks

"What name is given to the study of the similarities and differences between the bones and skeletal structures of animals, including fossils of extinct species?"

I put structural morphology but the answer was comparative anatomy. I'm not really understanding the difference between them, could someone explain this to me? Why would it not be structural morphology because I have it in my notes that it is the study of the structure of organisms. Also comparative anatomy is not a term used in the study design.

I also have another question for Q7c in the 2015 VCAA exam that asks

"In the rat pituitary gland, GC stimulates the production of the growth hormone protein. However, in the rat liver, GC stimulates the production of the enzyme tryptophan oxygenase. Given that the genetic sequence is identical in all somatic rat cells, explain how the production of distinct proteins in different cell types could occur."

I had no clue what to write and the answers say that factors expressed by regulator genes could lead to production of the different proteins. How can factors do that when the genetic sequence is identical in all rat cells? Do the factors cause different splicing in two different cells which results in two different proteins? I think I'm way off but I really can't understand this question and I don't think I'm alone cus 94% ppl got it wrong as well that year.



Thanks.

[Billuminati]

In the 2015 VCAA exam Q9b asks

"What name is given to the study of the similarities and differences between the bones and skeletal structures of animals, including fossils of extinct species?"

I put structural morphology but the answer was comparative anatomy. I'm not really understanding the difference between them, could someone explain this to me? Why would it not be structural morphology because I have it in my notes that it is the study of the structure of organisms. Also comparative anatomy is not a term used in the study design.

I also have another question for Q7c in the 2015 VCAA exam that asks

"In the rat pituitary gland, GC stimulates the production of the growth hormone protein. However, in the rat liver, GC stimulates the production of the enzyme tryptophan oxygenase. Given that the genetic sequence is identical in all somatic rat cells, explain how the production of distinct proteins in different cell types could occur."

I had no clue what to write and the answers say that factors expressed by regulator genes could lead to production of the different proteins. How can factors do that when the genetic sequence is identical in all rat cells? Do the factors cause different splicing in two different cells which results in two different proteins? I think I'm way off but I really can't understand this question and I don't think I'm alone cus 94% ppl got it wrong as well that year.



Thanks.

1st question is something to do with VCAAism, you must kiss their a*ses by memorising their preferred term + definition. This is also from 2015 which has a different study design from now.

For the 2nd question, I think it goes beyond the scope of VCE bio. I think you just need to be aware that although all cells in an eukaryote have the same genome, expression is highly diverse due to cell specialisation. If you want a uni molecular bio explanation, eukaryotic gene regulation involves enzymes called histone acetyltransferases (HAT) and histone deacetylases (HD). Histones are little basic proteins called histones around which DNA is wrapped in chromosomes. HAT gives ethyl groups to certain amino acid residues of histones, which poke out and somewhat decondenses the chromosome, exposing the promotor sequences like the TATA box for transcription initiation factors and RNAPII to bind (hence upregulating gene expression). HDs do the opposite, as their name suggests, they remove the ethyl group, causing the chromosome to condense and making the promotor sequence less accessible to the proteins/enzymes involved in transcription.

[Doogie38]

Hey, can someone clarify the meaning of melting temperature in DNA hybridisation? My textbook says its the temperature at which half of the double-stranded DNA sample becomes single-stranded, whereas my teachers notes state the temperature at which the DNA sample becomes single-stranded again. Is it half of the DNA or all of it?

Thank you

[mishyprzed1]

Hi!!!

Does anyone have any revision or any past/ practise SACs for Unit 4 AOS 1?  My SAC involves data analysis and I would appreciate any resources! Thank you

[Billuminati]

Hey, can someone clarify the meaning of melting temperature in DNA hybridisation? My textbook says its the temperature at which half of the double-stranded DNA sample becomes single-stranded, whereas my teachers notes state the temperature at which the DNA sample becomes single-stranded again. Is it half of the DNA or all of it?

Thank you

Tm is the temperature at which half of dsDNA becomes ssDNA. It's variable as GC content (G and C form 3 H bonds instead of 2 as in AT pairs so this increases Tm) as well as DNA length (longer= higher temp due to more H bonds) can affect it. Your teacher is referring to the DENATURATION temperature where all DNA is single stranded. This is usually a fixed value at 92-95°C

[Billuminati]

Hi!!!

Does anyone have any revision or any past/ practise SACs for Unit 4 AOS 1?  My SAC involves data analysis and I would appreciate any resources! Thank you

These were the practice SACs I was given when I did bio 3/4 in 2017, there are booklets organised by topic in this folder. I don't think they've changed the study design yet.

https://drive.google.com/drive/folders/1ELeD-HuLD5J6MMzX9i1rT0zNpbhb-Uw-

[priya_]

couple questions that I can't find answers for.

1. why are mutations in master genes rare?

2. explain the evolutionary significance of mast regulatory genes in the Galapagos finches.

3. describe one way that genes are regulated so that the same genes genes can produce appendages when genes are expressed in different locations in the artemia embryo.

thanks in advance.

[Billuminati]

couple questions that I can't find answers for.

1. why are mutations in master genes rare?

2. explain the evolutionary significance of mast regulatory genes in the Galapagos finches.

3. describe one way that genes are regulated so that the same genes genes can produce appendages when genes are expressed in different locations in the artemia embryo.

thanks in advance.

1. Because mutations in master genes usually lead to non-viable offspring ie they die in utero

2. Sorry I forgot all of my evolution theory lmao, been in biomed for too long

3. Alternative splicing, one gene can code for many proteins depending on which exons are retained or excised along with the introns after mRNA processing.

[Chocolatepistachio]

Can IPSPS only summate with IPSPS and EPSPs can only summate with EPSPs

[biology1234]

what is difference between reproductive and therapeutic cloning

[K.Smithy]

Can IPSPS only summate with IPSPS and EPSPs can only summate with EPSPs

Hey Chocolatepistachio,
With neural integration, the neuron will sum up all of the inputs that it receives through the synapses. As you would know, some of these are going to be excitatory whilst others will be inhibitory. Neurons can receive lots and lots of inputs in a given moment, yet no matter how many inputs they receive they can only produce one output (an action potential). If the sum of the inputs is high enough, an action potential will be triggered. Thus, IPSPs can sum with EPSPs to reduce the chance of a neuron firing an action potential.
I hope this helps
Katelyn

[specimen]

Q 25 from VCAA 2017 NHT asks:

A section of a DNA strand has the base sequence AGCGCATAGCAA.
During DNA replication to form the complementary DNA strand, a mutation involving a single base
substitution occurred in the last triplet of this section.
This mutation was then passed on to the mRNA when transcription of the complementary strand occurred.
The base sequence of the mRNA containing the mutation could be
A.    AGCGCAUAGCAA
B.    AGCGCAUAGUAA
C.    UCGCGUAUCGUU
D.    UCGCGUAUCAUU

The answer says it is D. I'm not sure if I'm confusing myself or I've read this question completely wrong but it says that a complementary DNA strand is formed during DNA replication and that is the strand that is transcribed. If I'm reading this correct then wouldn't the mRNA strand read AGCGCAUAGCAA and then the mutation causes the one of the nucleotides in the last codon to become UAA making it option B?

Please tell me if I'm on the wrong track. Thanks.

[-Lilac-]

Q 25 from VCAA 2017 NHT asks:

A section of a DNA strand has the base sequence AGCGCATAGCAA.
During DNA replication to form the complementary DNA strand, a mutation involving a single base
substitution occurred in the last triplet of this section.
This mutation was then passed on to the mRNA when transcription of the complementary strand occurred.
The base sequence of the mRNA containing the mutation could be
A.    AGCGCAUAGCAA
B.    AGCGCAUAGUAA
C.    UCGCGUAUCGUU
D.    UCGCGUAUCAUU

The answer says it is D. I'm not sure if I'm confusing myself or I've read this question completely wrong but it says that a complementary DNA strand is formed during DNA replication and that is the strand that is transcribed. If I'm reading this correct then wouldn't the mRNA strand read AGCGCAUAGCAA and then the mutation causes the one of the nucleotides in the last codon to become UAA making it option B?

Please tell me if I'm on the wrong track. Thanks.

This question pops up every year, it’s designed to trip you up. Here is how I think about it.

DNA strand:

AGCGCATAGCAA

Mutation occurs during DNA replication in the last codon:

TCGCGTATC(mutation)

The question then states ‘transcription of the complementary strand’. So the complementary strand of the above is:

AGCGCATAG(mutation)

Then that strand is transcribed into mRNA:

UCGCGUAC(mutation)

Gives D!

[specimen]

This question pops up every year, it’s designed to trip you up. Here is how I think about it.

DNA strand:

AGCGCATAGCAA

Mutation occurs during DNA replication in the last codon:

TCGCGTATC(mutation)

The question then states ‘transcription of the complementary strand’. So the complementary strand of the above is:

AGCGCATAG(mutation)

Then that strand is transcribed into mRNA:

UCGCGUAC(mutation)

Gives D!

"During DNA replication to form the complementary strand, a mutation occurred" So wouldnt it be that

Mutation occurs in the last codon to make TCGCGTATC     (this is the complementary strand formed during DNA replication)

And then it is this "complementary strand" that is transcribed which becomes AGCGCAUAGUAA? How am I supposed to know when they are saying that "transcription of the complementary strand occurred" they mean the complementary strand of the complementary DNA formed during replication? I read this as transcription of the same complementary DNA strand occurred.

[Stormbreaker-X]

How did you guys revise for biology exams? I wonder how do people revise so much content.