Yacoubb's Bio 3+4 Questions

[psyxwar]

- The ribosomes are assembled into a pre-defined sequence to form a desired polypeptide.

wat

Also tRNA triplets are anticodons

[Yacoubb]

wat

Also tRNA triplets are anticodons

Err lol I know that I need to learn to check over my responses - I was in the middle of answering a text & writing the response.

I meant the 'amino acids are assembled into a pre-defined sequence to form a desired polypeptide'.

3 concurrent tRNA bases = anti-codon.
3 concurrent mRNA bases = codon
3 concurrent DNA bases = triplet.

[vox nihili]

Okay so would this be better:

Translation:
- mRNA attaches to the ribosome, where it is read and translated.
- tRNA codons attach to the mRNA codons; the tRNA molecules carry amino acids to the ribosomes.
- The ribosomes are assembled into a pre-defined sequence to form a desired polypeptide.

As psyxwar has alluded to, you'd probably get in a little bit of trouble with some of the specifics there.

mRNA goes to the ribosome, this is true.
tRNA anticodons are complimentary to the mRNA codons. The tRNA molecule with the complimentary anticodon brings the amino acid it's bound to to the ribosome.
The way the sequence is actually created is by constant repetition of this process. The bond between the amino acid and the tRNA molecule is broken, whilst enzymes make a bond between it and the previous amino acid. The mRNA moves along, and the next codon is (let's say but not technically right) "shown". The tRNA molecule comes along, and we all know what happens there. Keeps on keeping on until the mRNA molecule is done.

It's really, really crappy to describe. But the key points are the mRNA gives the sequence, it's read at the ribosome, tRNA brings the amino acids and has a complimentary anticodon to the mRNA. These are the really key points. The actual mechanism for building the protein isn't well covered in the course.

[Yacoubb]

As psyxwar has alluded to, you'd probably get in a little bit of trouble with some of the specifics there.

mRNA goes to the ribosome, this is true.
tRNA anticodons are complimentary to the mRNA codons. The tRNA molecule with the complimentary anticodon brings the amino acid it's bound to to the ribosome.
The way the sequence is actually created is by constant repetition of this process. The bond between the amino acid and the tRNA molecule is broken, whilst enzymes make a bond between it and the previous amino acid. The mRNA moves along, and the next codon is (let's say but not technically right) "shown". The tRNA molecule comes along, and we all know what happens there. Keeps on keeping on until the mRNA molecule is done.

It's really, really crappy to describe. But the key points are the mRNA gives the sequence, it's read at the ribosome, tRNA brings the amino acids and has a complimentary anticodon to the mRNA. These are the really key points. The actual mechanism for building the protein isn't well covered in the course.

The assessment report says this from VCAA 2010:
- mRNA is read by the ribosomes.
- tRNA anti-codons attach to mRNA codons.
- A polypeptide is synthesised.

That gained the full marks ^^ I'm going to go with that. Is my transcription summary good though?

[vox nihili]

The assessment report says this from VCAA 2010:
- mRNA is read by the ribosomes.
- tRNA anti-codons attach to mRNA codons.
- A polypeptide is synthesised.

That gained the full marks ^^ I'm going to go with that. Is my transcription summary good though?

Good pick-up on that one. That would suffice obviously.

For your transcription answer, looking at the marking scheme you'd have lost a mark for failing to mention complimentary base pairing. It's important to note that the RNA strand is based on the DNA strand, as it really is the underpinning of gene expression. Otherwise, it's fine.

[Yacoubb]

Good pick-up on that one. That would suffice obviously.

For your transcription answer, looking at the marking scheme you'd have lost a mark for failing to mention complimentary base pairing. It's important to note that the RNA strand is based on the DNA strand, as it really is the underpinning of gene expression. Otherwise, it's fine.

But the marking scheme based upon the 2012 VCAA exam 2 said 'three' of the below and I had mentioned:
- DNA template strand being copied by RNA polymerase.
- pre-mRNA being produced that undergoes post-transcription modification.
- the introns are removed from the mRNA molecule, a poly-A tail is added at the 3'end of the mRNA molecule and a methyl cap is added at the 5'end of the mRNA molecule.
- the mRNA molecule leaves the nucleus.

^Surely my answer has 3 of the parts of the marking scheme?

[vox nihili]

But the marking scheme based upon the 2012 VCAA exam 2 said 'three' of the below and I had mentioned:
- DNA template strand being copied by RNA polymerase.
- pre-mRNA being produced that undergoes post-transcription modification.
- the introns are removed from the mRNA molecule, a poly-A tail is added at the 3'end of the mRNA molecule and a methyl cap is added at the 5'end of the mRNA molecule.
- the mRNA molecule leaves the nucleus.

^Surely my answer has 3 of the parts of the marking scheme?

It probably does, but the VCAA marking schemes aren't the full marking schemes. They're a fairly rough guide. I daresay that it being based on the complimentary strand of DNA is a fairly important thing, and it may cost you a mark. Having said that, it may not. I think there's probably reasonable doubt (there is in my mind), so I guess it can be improved!

[Yacoubb]

It probably does, but the VCAA marking schemes aren't the full marking schemes. They're a fairly rough guide. I daresay that it being based on the complimentary strand of DNA is a fairly important thing, and it may cost you a mark. Having said that, it may not. I think there's probably reasonable doubt (there is in my mind), so I guess it can be improved!

Oh okay then fair enough. I'll mentioned that the pre-mRNA molecule is formed by complementary base pairing. Would I need to add anything to that or would the bolded sentence be sufficient?

[vox nihili]

Oh okay then fair enough. I'll mentioned that the pre-mRNA molecule is formed by complementary base pairing. Would I need to add anything to that or would the bolded sentence be sufficient?

That'd be great. It really is nitpicking but it seems as though that's where you're at!

[Yacoubb]

That'd be great. It really is nitpicking but it seems as though that's where you're at!

Thanks t-rav. I need the nit-picking. Its those small things that could cost valuable marks! So I'll quickly list transcription and translation again and this is taking everything into consideration.

Transcription:
- The DNA template strand is copied by RNA polymerase.
- The pre-mRNA molecule is formed by complementary base pairing.
- The pre-mRNA molecule undergoes post-transcription modification, where introns are removed, a poly-A tail is added at the 3' end of the mRNA molecule and a methyl cap is added at the 5' end of the mRNA molecule.
- The mRNA molecule leaves the nucleus via the nuclear pores, entering the cytoplasm.

Translation:
- The mRNA molecule is read and translated by the ribosome.
- tRNA anti-codons attach to mRNA codons.
- tRNA molecules carry specific amino acids to the ribosome, where a polypeptide is then synthesised.

Question:
Would it be sufficient to say that the function of RNA polymerase is to copy the template strand of DNA to produce a pre-mRNA molecule, and that it is involved in transcription as an enzyme?

And would these be sufficient:
mRNA:
Carries the genetic code from the nucleus to the ribosomes.

tRNA:
Carries a specific amino acid to the ribosome.

Why is pre-mRNA longer than mRNA?
* pre-mRNA contains both introns and exons.
* Following post-transcription modification, the introns are removed, making the mRNA strand shorter.

[vox nihili]

Thanks t-rav. I need the nit-picking. Its those small things that could cost valuable marks! So I'll quickly list transcription and translation again and this is taking everything into consideration.

Transcription:
- The DNA template strand is copied by RNA polymerase.
- The pre-mRNA molecule is formed by complementary base pairing.
- The pre-mRNA molecule undergoes post-transcription modification, where introns are removed, a poly-A tail is added at the 3' end of the mRNA molecule and a methyl cap is added at the 5' end of the mRNA molecule.
- The mRNA molecule leaves the nucleus via the nuclear pores, entering the cytoplasm.

Translation:
- The mRNA molecule is read and translated by the ribosome.
- tRNA anti-codons attach to mRNA codons.
- tRNA molecules carry specific amino acids to the ribosome, where a polypeptide is then synthesised.

Question:
Would it be sufficient to say that the function of RNA polymerase is to copy the template strand of DNA to produce a pre-mRNA molecule, and that it is involved in transcription as an enzyme?

And would these be sufficient:
mRNA:
Carries the genetic code from the nucleus to the ribosomes.

tRNA:
Carries a specific amino acid to the ribosome.

Why is pre-mRNA longer than mRNA?
* pre-mRNA contains both introns and exons.
* Following post-transcription modification, the introns are removed, making the mRNA strand shorter.

That all looks fine. Though you don't need to say the last bit about RNA polymerase. Just that it synthesises pre-mRNA from DNA

The remarks about pre-mRNA and mRNA are completely correct too, and I think your definitions of the different RNAs are sufficient as well!

[Yacoubb]

That all looks fine. Though you don't need to say the last bit about RNA polymerase. Just that it synthesises pre-mRNA from DNA

The remarks about pre-mRNA and mRNA are completely correct too, and I think your definitions of the different RNAs are sufficient as well!

Okay fair enough Thanks so much!

How much do we need to know in regards to linked genes? Would it be sufficient to know about how the chances of recombinant gametes decreasing the closer the loci of two particular genes?

[vox nihili]

Okay fair enough Thanks so much!

How much do we need to know in regards to linked genes? Would it be sufficient to know about how the chances of recombinant gametes decreasing the closer the loci of two particular genes?

Hmm I'm not really sure! I can't remember much about linked genes to be honest. I think you'd need to just appreciate how they affect probabilities of certain phenotypes. I'm not entirely sure what you mean by recombinant gametes though?

[alondouek]

How much do we need to know in regards to linked genes? Would it be sufficient to know about how the chances of recombinant gametes decreasing the closer the loci of two particular genes?

You should be familiar with the technique of performing a dihybrid cross with linked genes (as opposed to the more conventional unlinked gene dihybrid cross, which you've likely already covered!).

I don't know if it is still part of the course, but if it is then learn the basic techniques behind gene mapping with linked genes (e.g. distance between two loci relating to probability of recombination).

[vox nihili]

You should be familiar with the technique of performing a dihybrid cross with linked genes (as opposed to the more conventional unlinked gene dihybrid cross, which you've likely already covered!).

I don't know if it is still part of the course, but if it is then learn the basic techniques behind gene mapping with linked genes (e.g. distance between two loci relating to probability of recombination).

The first part of what you've said is definitely it. It's all coming back to me now haha

I don't think the second part is relevant though. I never learned it, that's for sure.