OCR 2010 A2 Biology Unit 2 - Control, Genome and Environment Watch

Mona Lisa
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#3621
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#3621
(Original post by DR_X)
I was fine until I went on TSR......now I feel like banging my head.............
I'm the opposite lol at first I felt like calling brunel and telling them to just put me out of my misery and reject me now, but now I think I've done ok-ish especially after reading all this stuff about UMS and raw marks. I've just gotta ace the rest of my exams.

HOPEFULLY WE ALL DID FINE!!
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DR_X
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#3622
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#3622
(Original post by Varciani)
Yeah if it was taken from the middle of a codon, not if it was at the start of one, it would only delete 7 amino acids and leave the rest unchanged.

But yeah, that makes sense too. It was a suggest question though so there should be plenty of right answers
but I only worked that out after your post.......FML.....
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toxik_apple
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#3623
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#3623
I just realised in the 'compare the two fly heads' question I forgot to state which figure I was using, like: figure 1 has antenna whereas figure 2 has antennapedia.
FML :sad:
OCR's harsh, and the mark will be given for stating the pictures. Shoot.

I want to go on pg 181 to see if there's more about UMS, but I'm too scared about what I may see there. lol
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_lynx_
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#3624
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#3624
(Original post by Varciani)
Oh and would I be right with this for the base substitution, 21 base pair deletion or 13 base pair deletion:

13 Base pair deletion would cause most change to the gene as it would not only remove 4 codons from the translation sequence - and so remove 4 amino acids from the polypeptide - but it would also remove a base from the next codon, leaving it with 2. So a base would be taken from the next codon to solve that, and this continues to the end of the gene, changing every subsequent codon, and so changing every subsequent amino acid too'?? Not seen anyone comment on this question and imo it was the hardest one on the paper!
When referring to 13 base pair deletion, I thought they meant the 13th base pair. Am I correct in assuming that?

I said it would be the 13 base pair deletion, because it would cause more amino acids to be altered due to frame shift.
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matt7
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#3625
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#3625
(Original post by InvoluntarySlacker)
That really confused me. I had a suspicion it was 13 with something to do with number of codons but couldn't figure it out. Hope i got at least one mark for saying frame shift.
Frameshift was probably worth a mark
The single substitution could have been silent, or at most it would have resulted in one amino acid difference in the primary structure.
The 21 base deletion would have resulted in exactly 7 amino acids being lost from the primary structure, but no frameshift.
The 13 base deletion was not a multiple of 3, so it would have caused a frameshift and affected everything following it.


(Original post by v1oXx-)
I think I lost over 20 marks, but by my calculations, if it's 66/100 for an A, and 59 for an A (going on last year), 80/100 will be 150/150 UMS. Maybe it'll be a bit higher.
You really reckon the boundaries will be so low again? I've heard last year was really really nasty for it to be that low, whereas the general consensus for this exam seem to be that it wasn't too horrendous.
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franchango
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#3626
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#3626
(Original post by Varciani)
Oh and would I be right with this for the base substitution, 21 base pair deletion or 13 base pair deletion:

13 Base pair deletion would cause most change to the gene as it would not only remove 4 codons from the translation sequence - and so remove 4 amino acids from the polypeptide - but it would also remove a base from the next codon, leaving it with 2. So a base would be taken from the next codon to solve that, and this continues to the end of the gene, changing every subsequent codon, and so changing every subsequent amino acid too'?? Not seen anyone comment on this question and imo it was the hardest one on the paper!
YES that's what I put! Because 21 is divisible by three so would just delete 7 amino acids and leave it at that. Removing one base only causes a frameshift. But removing 13 gets rid of 4 amino acids AND causes a frameshift and so has the biggest effect.
Boom
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Varciani
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#3627
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#3627
(Original post by _lynx_)
When referring to 13 base pair deletion, I thought they meant the 13th base pair. Am I correct in assuming that?

I said it would be the 13 base pair deletion, because it would cause more amino acids to be altered due to frame shift.
Do you mean just deleting the 13th base pair alone? If so, I don't think that that was what the question initially intended, but yeah the end result is still basically the same - massive frameshift throughout the rest of the gene.
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DR_X
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#3628
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#3628
(Original post by franchango)
YES that's what I put! Because 21 is divisible by three so would just delete 7 amino acids and leave it at that. Removing one base only causes a frameshift. But removing 13 gets rid of 4 amino acids AND causes a frameshift and so has the biggest effect.
Boom
why does it have to be exactly 7 triplets?.........:confused:
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MadMaths
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#3629
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#3629
(Original post by franchango)
YES that's what I put! Because 21 is divisible by three so would just delete 7 amino acids and leave it at that. Removing one base only causes a frameshift. But removing 13 gets rid of 4 amino acids AND causes a frameshift and so has the biggest effect.
Boom

yesssssssss
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_lynx_
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#3630
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#3630
(Original post by Varciani)
Do you mean just deleting the 13th base pair alone? If so, I don't think that that was what the question initially intended, but yeah the end result is still basically the same - massive frameshift throughout the rest of the gene.
Oh dear, may have fluked the correct answer after reading what others have put. I won't get full marks for it though.
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DR_X
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#3631
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#3631
we need a bio genius to do a TSR mark scheme.........rep will be given....
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InvoluntarySlacker
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#3632
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#3632
(Original post by matt7)
Frameshift was probably worth a mark
The single substitution could have been silent, or at most it would have resulted in one amino acid difference in the primary structure.
The 21 base deletion would have resulted in exactly 7 amino acids being lost from the primary structure, but no frameshift.
The 13 base deletion was not a multiple of 3, so it would have caused a frameshift and affected everything following it.



You really reckon the boundaries will be so low again? I've heard last year was really really nasty for it to be that low, whereas the general consensus for this exam seem to be that it wasn't too horrendous.
Hahaha I am an idiot. I remember counting the numbers to see if they were multiples of 3. I was in a rush (thought I had 15 mins instead of 30) and assumed 13 was a multiple. So I was confused for a while thinking...whut? So I thought the 21 deletion would be more catastrophic. If I spent an extra minute I would have gotten the answer. :facepalm2:
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InvoluntarySlacker
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#3633
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#3633
(Original post by Darthdevidem)
So no-one else wrote GENETIC DRIFT for the "Impulsive" allele one?
Yeah I did. What's so advantageous about a person with ADHD?

Genetic drift was the only explanation.
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v1oXx-
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#3634
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#3634
****. I put a 13 base pair deletion, then right at the end, I crossed out 13 and put 21.
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AnthonyShock
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#3635
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#3635
(Original post by steph_v)
I don't think it will. It was 2 marks, I'd assume you get one mark for 'electron microscope' and 1 mark for 'scanning'. Unfortunately I just put transmission electron microscope as a guess.
Aaaah no way?

It was two marks?? :eek:
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george54
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#3636
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#3636
(Original post by InvoluntarySlacker)
Yeah I did. What's so advantageous about a person with ADHD?

Genetic drift was the only explanation.
eh... for 4 marks? i dont think so. one maybe... behavioral selection pressure in favour of those with an impulsive persoanlity perhaps? girls prefering a guy thats spontaneous?
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pgreg1
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#3637
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#3637
I put that a mutation caused the variation of DRD4 gene which gives impuslive and explorative behaviour. These people were more likely to seek out new habitats. The environment changed so that the old habitat become uninhabitable to humans so only those with that particular DRD4 gene survived (directional selection). Because there was a high allele frequency of those people in the population, it was passed on to their offspring.

Dunno if that's right though, not too confident!
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AnniG
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#3638
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#3638
(Original post by InvoluntarySlacker)
Yeah I did. What's so advantageous about a person with ADHD?

Genetic drift was the only explanation.
People who explore more may be more likely to come across food etc. Maybe people who are impulsive could be more successful in life too (eg. in business - since it said humans - and successful people are more attractive to mate with)?
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InvoluntarySlacker
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#3639
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#3639
(Original post by george54)
eh... for 4 marks? i dont think so. one maybe... behavioral selection pressure in favour of those with an impulsive persoanlity perhaps? girls prefering a guy thats spontaneous?
:iiam:

You could have also said they all have big dicks.

But you could have gotten 4 marks for elaborating the genetic drift theory.
That's around 3 marks together and an example would have given you the fourth mark.

But they could all been valid marks. I did say impulsive behaviour is attractive to some people of the opposite sex.
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TillyOB
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#3640
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#3640
Haha I definitely wrote about latent learning in that one too, then evolution. Thanks OCR again. Loads of marks on dopamine. I guess it was that or gorillas.
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