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F215 - Revision thread 13th June 2011

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Reply 1400

Waqar Y

Original post by Kidms001

What sort of scores are people hitting on the past papers? :s-smilie:

About 65-75, you?

Reply 1401

sportycricketer

Why is everyone so worried about PCR? Isn't that just that the process of DNA amplification via diff temperatures? :s-smilie:

Reply 1402

Waqar Y

Original post by sportycricketer

Why is everyone so worried about PCR? Isn't that just that the process of DNA amplification via diff temperatures? :s-smilie:

I think it's got something to do with the question that came up in January, it was a really hard one as well and 9 marks :|

Reply 1403

intellectual1

Original post by Kidms001

What sort of scores are people hitting on the past papers? :s-smilie:

dont worry too much...there's 5 marks between the E and D...and 6 marks between the A to B, B to C, C to D...it is matter of 6 marks on average that differentiates between each grade...ie the E is as alow as 37 - 40 whilst the A has been at 59 and 60 respectively in the Jan and Jun sessions...

Reply 1404

entertheOJI

Original post by Waqar Y

About 65-75, you?

only done the January 2011 paper - got 70. I've still got a few things to revise tho.

Jan 2011 had very little of plants and plant hormones, i believe there were only 5 marks in total, so i'm guessing that will come up on Monday.

Reply 1405

kabolin

Original post by YuDunno

I can't remember the question, I remember missing it out though :confused:

maybe it will so.. go on.

Outline PCR :biggrin:

.....

heat the dna to 95 degrees to break hydrogen bonds between complementary bases to produce to single strands of dna.
cool to 55 degrees to allow primers to complementary base pair with the 3' and 5' end. this allows dna polymerase to now bind onto the primers.
heat to 72degrees(optimum temp for dna polymerase) it can now form hydrogen bonds with complementary bases on each single stranded dna.
the enzyme is thermophillic.
you now have 2 copies of the same dna. this process may be repeated.

Reply 1406

Nirgilis

Original post by Waqar Y

About 65-75, you?

About the same. Have you done the specimen paper?

Reply 1407

sportycricketer

Original post by Waqar Y

I think it's got something to do with the question that came up in January, it was a really hard one as well and 9 marks :|

I've done the Jan paper, Do you remember what question is it? :/

Reply 1408

Waqar Y

Original post by sportycricketer

I've done the Jan paper, Do you remember what question is it? :/

Was the one where you had to compare PCR to in vivo something to do with bacteria

Reply 1409

Waqar Y

Original post by Kidms001

About the same. Have you done the specimen paper?

Yeah I think i got 75 or something for that, it was okay, you?

Reply 1410

sportycricketer

Original post by Waqar Y

Was the one where you had to compare PCR to in vivo something to do with bacteria

oh yeah that one! That was a such a stupid qs with a stupid markscheme which isnt in our spec at all! It contradicted both ideas but surely it wont be tested again considering it was recent? :s-smilie:

but I dont know

Reply 1411

YuDunno

Original post by Waqar Y

Erm, shows how human activity affected the habitats on the island.

increase in people going as tourists, led to the increase of buildings > which led to the destruction of habitats and also the loss of biodiversity.

increase in people = increase in pollution which also decreased biodiversity of habitats due to waste being dumped.

also, hunting for giant sea tortioise populations also led to giant sea tortoise population falling as well.

erm, what else - introduction of non native species, e.g goat led to interspecific competition between goat and giant tortoise, which was outcompeted