VCE Biology Question Thread

[cosine]

RNA primase

It's actually DNA primase, which is a RNA Polymerase enzyme. They call is DNA Primase because it synthesises a primer onto the DNA template strand, and it's an RNA polymerase enzyme in reality because as we know, RNA polymerase can only synthesise nucleic acids without primers, and if you think about it, if youre synthesising and attaching primers onto DNA, there is no initial primer to commence this, so it must be RNA polymerase (DNA primase).

As for my earlier question, are primers always passively attached to the DNA templates in PCR?
Also, does DNA Primase directly synthesise the primer onto the beginning region of the template DNA strand?

[Biology24123]

It's actually DNA primase, which is a RNA Polymerase enzyme. They call is DNA Primase because it synthesises a primer onto the DNA template strand, and it's an RNA polymerase enzyme in reality because as we know, RNA polymerase can only synthesise nucleic acids without primers, and if you think about it, if youre synthesising and attaching primers onto DNA, there is no initial primer to commence this, so it must be RNA polymerase (DNA primase).

As for my earlier question, are primers always passively attached to the DNA templates in PCR?
Also, does DNA Primase directly synthesise the primer onto the beginning region of the template DNA strand?

DNA primase adds an RNA primer. And yes, DNA primase is a type of RNA polymerase

[BakedDwarf]

What definition of genetic screening does VCAA expect?

All i know is that it's used to :
- identify chromosome abnormalities and inherited conditions in embryos
- determine if a person is a carrier of a condition or is likely to develop the condition later in their life time

[cosine]

DNA primase adds an RNA primer. And yes, DNA primase is a type of RNA polymerase

But you said RNA primase earlier? Am i missing something?

[warya]

DNA primase adds an RNA primer. And yes, DNA primase is a type of RNA polymerase

This is really confusing

[vox nihili]

It's actually DNA primase, which is a RNA Polymerase enzyme. They call is DNA Primase because it synthesises a primer onto the DNA template strand, and it's an RNA polymerase enzyme in reality because as we know, RNA polymerase can only synthesise nucleic acids without primers, and if you think about it, if youre synthesising and attaching primers onto DNA, there is no initial primer to commence this, so it must be RNA polymerase (DNA primase).

As for my earlier question, are primers always passively attached to the DNA templates in PCR?
Also, does DNA Primase directly synthesise the primer onto the beginning region of the template DNA strand?

To answer your second question first, the start of the gene is primed. The primer defines the boundaries of the gene (at least as far as transcription is concerned).
As to your first, yes. We don't use primase because that would be expensive and would complicate things. For one ,we'd have to get a thermostable primase. Plus, we can make primers with better accuracy than primase, so why bother?
The reason they're made as new in DNA replication is because there is literally no point devoting energy to making primers that won't be needed in the cell. So in DNA replication, they make them on-demand.

[adnauseam]

Brow ridges may have provided protection to the skull during brachiation when ancestors of hominins were tree-dwelling.

Would these definitions be alright, i took some from the vcaa definitions document, but others im not sure about.
1. Signal transduction: The binding of the ligand to specific receptor (which has complementary shape to ligand) initiates the transfer of the external signal into the cell, involving a cascade of events and relay molecules, resulting in a specific internal cellular response


2. Protein structures:
a.   Primary: specific sequence of amino acids in a polypeptide chain
b.   Secondary: the coiled or pleated structure in a polypeptide chain (including α-helices and β-pleated sheets)

c.   Tertiary: the overall 3D structure in a polypeptide chain
composed of secondary structures
d.   Quaternary: the way in which two or more polypeptide chains joined together

3.   Natural Reservoir: animal that can harbour pathogen in the wild without suffering from the disease

4.   Vaccine: artificially-prepared biological solution containing dead/attenuated forms of a pathogen or its subunits, intended to trigger a specific immune response

5.   Reflex arc: neuronal pathway that does not involve input from brain, thus response to original time is involuntary and response time is reduced.

And a process:
Speciation (allopatric):

•   Two populations are divided by geographic barrier with no gene flow between them
•   Each group experiences different selection pressures in their respective environments and different mutations accumulate, which allow differences in allele frequencies to develop
•   Over time, the populations, if reintroduced, would be unable to produce viable fertile offspring together

[Bruzzix]

What is the difference between a genetically modified and transgenic organism?

[vox nihili]

Brow ridges may have provided protection to the skull during brachiation when ancestors of hominins were tree-dwelling.

Would these definitions be alright, i took some from the vcaa definitions document, but others im not sure about.
1. Signal transduction: The binding of the ligand to specific receptor (which has complementary shape to ligand) initiates the transfer of the external signal into the cell, involving a cascade of events and relay molecules, resulting in a specific internal cellular response


2. Protein structures:
a.   Primary: specific sequence of amino acids in a polypeptide chain
b.   Secondary: the coiled or pleated structure in a polypeptide chain (including α-helices and β-pleated sheets)

c.   Tertiary: the overall 3D structure in a polypeptide chain
composed of secondary structures
d.   Quaternary: the way in which two or more polypeptide chains joined together

3.   Natural Reservoir: animal that can harbour pathogen in the wild without suffering from the disease

4.   Vaccine: artificially-prepared biological solution containing dead/attenuated forms of a pathogen or its subunits, intended to trigger a specific immune response

5.   Reflex arc: neuronal pathway that does not involve input from brain, thus response to original time is involuntary and response time is reduced.

And a process:
Speciation (allopatric):

•   Two populations are divided by geographic barrier with no gene flow between them
•   Each group experiences different selection pressures in their respective environments and different mutations accumulate, which allow differences in allele frequencies to develop
•   Over time, the populations, if reintroduced, would be unable to produce viable fertile offspring together

1. Yep, that's pretty well it. It's probably a little too specific though.

2. Primary is fine, secondary don't forget random coils, tertiary isn't the overall 3D structure of a protein, it's the overall shape of a polypeptide chain. To say it's composed of secondary structures is probably somewhat misleading too. Quarternary is spot on, basically.

3. pretty sure this is fine, I'll leave it to others to arc up if it's wrong

4. Your description of what comprises a vaccine is excellent, but you need to add "for the purposes of protecting the individual against infection by a particular pathogen". Strictly speaking this is actually not true of a vaccine but it's how they'd ask oyu to define it for VCE

5. you need to elaborate on this a bit more, describe what it is. Plenty of neuronal pathways don't involve the brain

allopatric speciation all good

[The Peasant]

What is the difference between a genetically modified and transgenic organism?

A transgenic organism is a subset of a genetically modified organism.

More specifically, a transgenic organism must contain genes/genetic information from another organism of different species. The foreign/implemented gene is then expressed by the "host organism".

In contrast, a genetically modified organism may/may not contain genetic information from another organism. As long as its genetic information has been tampered/altered in any artificial way possible, the organism is now called a genetically modified organism.

[cosine]

What is the difference between a genetically modified and transgenic organism?

Transgenic organisms are organisms where their genome has been altered in the way that they express the artificial genome as it's implemented in their own cell's DNA.

Genetically modified organisms is such that the artificial DNA is not implemented in their genome, for example when plasmids are inserted into bacterial cells, this recombinant plasmid does not interfere with the main chromosomal DNA of the bacteria.

[Bruzzix]

Transgenic organisms are organisms where their genome has been altered in the way that they express the artificial genome as it's implemented in their own cell's DNA.

Genetically modified organisms is such that the artificial DNA is not implemented in their genome, for example when plasmids are inserted into bacterial cells, this recombinant plasmid does not interfere with the main chromosomal DNA of the bacteria.

I don't think that's right because GMO's do have their genome changed. Although recombinant plasmids don't affect the bacteria's chromosome you can have recombinant plasmids change the genome of plants for example by inserting genetic material into the plants chromosome.

[Bruzzix]

Also what is the answer to this question?

[vox nihili]

A transgenic organism is a subset of a genetically modified organism.

More specifically, a transgenic organism must contain genes/genetic information from another organism of different species. The foreign/implemented gene is then expressed by the "host organism".

In contrast, a genetically modified organism may/may not contain genetic information from another organism. As long as its genetic information has been tampered/altered in any artificial way possible, the organism is now called a genetically modified organism.

Transgenic organisms are organisms where their genome has been altered in the way that they express the artificial genome as it's implemented in their own cell's DNA.

Genetically modified organisms is such that the artificial DNA is not implemented in their genome, for example when plasmids are inserted into bacterial cells, this recombinant plasmid does not interfere with the main chromosomal DNA of the bacteria.

I don't think that's right because GMO's do have their genome changed. Although recombinant plasmids don't affect the bacteria's chromosome you can have recombinant plasmids change the genome of plants for example by inserting genetic material into the plants chromosome.

The Peasant's answer is correct.

Also what is the answer to this question?
(Image removed from quote.)

This question shouldn't be asked on a VCE exam. The answer is dominant epistasis though.

[Bruzzix]

This question shouldn't be asked on a VCE exam. The answer is dominant epistasis though.

The answer was D. Recessive epistasis. Can you explain why?