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gingerandice
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#2841
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#2841
why cone cells and rod cells detect light of different intensities- no retinal convergence occurs with cone cells , and only light of high intensity is sufficient enough to break down iodopsin with would result in the creation of a generation potential. with rod cells, retinal convergence occurs, and light of low intensity if sufficient enough to cause the breakdown of rhodopsin, which creates a generator potential.
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estudiante_numero1
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#2842
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(Original post by Hippokrates)
If you do 4 up to 6 mark question standard you're good
Thanks for the reply! To clarify, is that 4-6 marks on each point we choose that is listed on the mark scheme? The mark schemes usually have three different key areas, with lots of points listed under all three. Do we just have to think of at least one point in each key area and write a typical 4-6 mark answer in order to get around 14/16?

Thanks again!


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GinaS
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#2843
(Original post by stoppy123)
My guess:

Mutation and it's consequences
- Define it.
- Types of it.
- What is can be caused by (mutagenic agents)
- Can lead to ineffective enzymes proteins etc.
- Causes speciation (mention all the steps)
- Causes adaptation
- Causes anti-biotic resistance.
- Makes variation within a population
- Can be advantageous, Sickle cell anemia + Malaria.
- Can be disadvantageous, Cystic fibrosis.
- May not do anything (degenarative nature of DNA)
- Can cause cancer by mutating tumour suppressors/proto-oncogenes.
I hope it is that!!


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gingerandice
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I can accept that all the fragments end with the same terminator nucleotide, but if its so 'random' why cant it end with a normal dna nucleotide?
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stoppy123
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#2845
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(Original post by gingerandice)
why cone cells and rod cells detect light of different intensities- no retinal convergence occurs with cone cells , and only light of high intensity is sufficient enough to break down iodopsin with would result in the creation of a generation potential. with rod cells, retinal convergence occurs, and light of low intensity if sufficient enough to cause the breakdown of rhodopsin, which creates a generator potential.
I've not learnt about iodopsin.

I've just thought:

Rod cells:
Able to converge onto one neurone, meaning less light is needed to create an actional potential.
Less acuity due to many rod cells going onto one neurone, meaning things are hard to tell apart.
Monochromatic vision

Cone cells:
One neurone attached to one cone cell, meaning a lot more light is needed to create an action potential,
Better acuity as cone cells have individual neurones.
Trichromatic vision
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SusieShire
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#2846
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Did anyone else take the Specimen Paper and find it really difficult? The first half was OK but the second half almost killed me. Got 6/15 on the IAA question! I hope the real paper is easier than that one...
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gingerandice
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(Original post by stoppy123)
I've not learnt about iodopsin.

I've just thought:

Rod cells:
Able to converge onto one neurone, meaning less light is needed to create an actional potential.
Less acuity due to many rod cells going onto one neurone, meaning things are hard to tell apart.
Monochromatic vision

Cone cells:
One neurone attached to one cone cell, meaning a lot more light is needed to create an action potential,
Better acuity as cone cells have individual neurones.
Trichromatic vision
oh? I have the nelson thrones textbook, it has the pigment stuff in it
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pjanoo
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#2848
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#2848
(Original post by James A)
Aim for around 6 topics. Make sure your paragraphs are straight to the point too. I guess getting my script back has helped me to see where I went wrong in the essay.


Also, the more you can cover of the syllabus, the better. The purpose of the synoptic paper is to see how much information you can relate and recall in an essay structure.
So would you say it's better to cover a wide variety of areas with less depth than to cover a few select areas with a greater amount of detail?
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Mocking_bird
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#2849
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#2849
(Original post by gingerandice)
I can accept that all the fragments end with the same terminator nucleotide, but if its so 'random' why cant it end with a normal dna nucleotide?
It can only end with a normal nucleotide if it has reached the very end of the dna fragment.
It ends with a modified nucleotide because that modified nucleotides prevents any further synthesis from occurring.
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tn234
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#2850
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#2850
Is it worth looking over the legacy papers to practise questions or to just focus on the new spec past papers?
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Hippokrates
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#2851
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(Original post by SusieShire)
Did anyone else take the Specimen Paper and find it really difficult? The first half was OK but the second half almost killed me. Got 6/15 on the IAA question! I hope the real paper is easier than that one...
I got about 50% and I'm predicted an A* :P Not that I'm going to get one because of this silly essay
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aWildPidgey
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#2852
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#2852
(Original post by stoppy123)
4 tubes containing DNA polymerase, the required fragment, free nucleotides and a terminator base, whether it be A, G, T or C.

Let's say the dna fragment you want is CGAATCGTTA.

In the first tube, using terminator A, you'll get fragments CGA, CGAA, CGAATCGTTA.
In the second tube, using terminator G, you'll get fragments CG CGAATCG
In the third tube, using terminator T, you'll get fragments CGAAT CGAATCGT CGAATCGTT
In the fourth tube, using terminator C, you'll get fragments C CGAATC

When these fragments are seperated on a gel, it will show the order in which the bases go, as you can read from the bottom up.
I think this might be wrong

The Sagner method attaches nucelotides to the DNA fragment to be sequenced, to find the complementary base sequence, and then the complementary sequence to that is the original base sequence of the DNA fragment.

When using A* terminator nucleotides (as above), you would get the fragments:
GCTTA*
GCTTAGCA*
GCTTAGCAA*

To find the original base sequence you work out the complementary sequence to the one you get from the Sagner method

At least from what I've read today this is right
please don't crucify if it's not :{
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F1's Finest
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#2853
(Original post by pjanoo)
So would you say it's better to cover a wide variety of areas with less depth than to cover a few select areas with a greater amount of detail?
yeah. You wanna show the examiner you can relate the essay title to various topics, not just a couple.
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pjanoo
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(Original post by SusieShire)
Did anyone else take the Specimen Paper and find it really difficult? The first half was OK but the second half almost killed me. Got 6/15 on the IAA question! I hope the real paper is easier than that one...
Haha yeah don't worry, it's just a specimen so it wouldn't have been standardised to the degree that a real paper is. That's why the mark scheme was so limited, on a real mark scheme we see so many different points and 'additional notes' that would be accepted because it's constantly being modified as more papers are moderated, don't judge your performance on that!
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stoppy123
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#2855
(Original post by aWildPidgey)
I think this might be wrong

The Sagner method attaches nucelotides to the DNA fragment to be sequenced, to find the complementary base sequence, and then the complementary sequence to that is the original base sequence of the DNA fragment.

When using A* terminator nucleotides (as above), you would get the fragments:
GCTTA*
GCTTAGCA*
GCTTAGCAA*

To find the original base sequence you work out the complementary sequence to the one you get from the Sagner method

At least from what I've read today this is right
please don't crucify if it's not :{
Yeah I realised after I did it that I did the wrong sequence, forgot they were supposed to be complementary, such a novice mistake !
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gingerandice
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(Original post by tn234)
Is it worth looking over the legacy papers to practise questions or to just focus on the new spec past papers?
you would be surprised by the way questions are repeated.
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stoppy123
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(Original post by gingerandice)
oh? I have the nelson thrones textbook, it has the pigment stuff in it
Hmm, maybe pigment stuff is required then? I don't have the nelson thrones book so I don't know >.<
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aWildPidgey
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#2858
(Original post by stoppy123)
Yeah I realised after I did it that I did the wrong sequence, forgot they were supposed to be complementary, such a novice mistake !
haha well you won't make it again then in the exam!
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pjanoo
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(Original post by James A)
yeah. You wanna show the examiner you can relate the essay title to various topics, not just a couple.
Okay thanks very much would you mind advising me on the best way I could go about getting up to speed with various topics, would you say just attempting all 8 past essays would be practise enough?
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pjanoo
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(Original post by stoppy123)
Hmm, maybe pigment stuff is required then? I don't have the nelson thrones book so I don't know >.<
It's not required
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