AQA BIOL2 Biology Unit 2 Exam - 26th May 2011

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Reply 600

??????????????????

Original post by lolo-x

omgomgomgomg i'm suddenly very panicked about this exam. has anyone found or made any good summary notes?

Found some on TSR. Not sure how to send. Can't find them again.

Reply 601

nasira372

Would there be any point in doing older papers before jan 2009?

Reply 602

??????????????????

Original post by parallal

I just want to make sure I have the stages of the cell cycle/mitosis right.

Interphase - G1, S, G2, M. DNA replication occurs during S phase. (Also ATP production)
Prophase - Nuclear envelope breaks down. The chromosomes condense/shorten/uncoil and become visible.
Metapahse - Spindle forms. Chromatids attach to spindle by their centromere and line up at the centre/equator of the cell.
Anaphase - Spindle contracts/shorten and separate the chromatids, pulling them to opposite poles.
Telophase - Nuclear envelope develops, chromosomes coil up and become invisible again.

Am I missing anything?

One thing you COULD add is that interphase also has the cell carrying out it's normal functions too. That's at G0.

Reply 603

oHellno

Original post by lolo-x

so why does the number of chromosomes stay the same shouldn't it double during interphase and then return to normal at telophase?

Yeah it's a bit weird. But when mitosis starts, each chromosome is made up of two sister chromatids, they're genetically identical. At the end of mitosis, those sister chromatids are pulled apart, they divide at the centromere. It's kind of weird to explain, but if you counted all the 'X's at prophase it's the same as the '|' at telophase.

Reply 604

Master.K

Original post by ??????????????????

Got chemistry and economics the day after... D:

So do I!

Chem2 and Eco2?

Reply 605

jbop

I'm doing June 2010 past paper now, it's grim.

Reply 606

??????????????????

Original post by Master.K

So do I!

Chem2 and Eco2?

Yup AQA and WJEC.

Reply 607

parallal

Original post by Mina!SS

I'm a bit confused. I thought at Telophase, the chromosomes have seperated to opposite poles and have formed two new cells with identical genetic material. so how can can it have the same number of choromosomes as prophase and half mass of DNA? :s-smilie:

Not the chromosomes, the chromatids have separated.

This is a definition of chromatid: Either of the two strands joined together by a single centromere, formed from the duplication of the chromosome during the early stages of cell division and then separate to become individual chromosome during the late stages of cell division.

So one chromosome forms two chromatids which are separated to form one chromosome so the number of chromosomes is unchanged.

It has half the mass of DNA because the DNA is doubled and shared between the two cells.

I'm sorry if I'm confusing you even further. :colondollar:

(edited 12 years ago)

Reply 608

fretter778

Original post by jsmith6131

If Fe2+ is green and haemoglobin contains Fe2+ why is our blood red

Because it's combined with O2 and oxidised to be red

Reply 609

parallal

Original post by ray of hope :)

sounds textbook to me, good job :smile:

Original post by ??????????????????

One thing you COULD add is that interphase also has the cell carrying out it's normal functions too. That's at G0.

Thanks. (:
Mitosis really messed me up in the last exam. I'm determined to not let it get the better of me this time.

Reply 610

TlanTlan

Edexcel stats was on friday and by the look of it i aced that. I have c2 in the morning though :frown:

Reply 611

oHellno

Original post by jbop

I'm doing June 2010 past paper now, it's grim.

Jan 2011 is horrific.

Reply 612

LifeIsGood

Original post by oHellno

So at interphase it replicates, prophase contains the replicated DNA so when Anaphase takes place, it halves?

Reply 613

liviaaa

Original post by ScienceGeek3

I have the same as you PLUS economics on Friday along with chem 2, I think I win :tongue:

Ohhh that's bad! Yes you win. :tongue:

Reply 614

liviaaa

Original post by HaimishaParekh

Oh my! Thank god, Biol2 is my last exam :biggrin:

Good luck for yours though!

Thanks, you too :smile:

I also have 1 exam after half term!

Reply 615

lolo-x

Original post by LifeIsGood

what do you need help with?

I don't think there's one particular area, although I would say meiosis is the most difficult part for me.
I am just worrying that I haven't covered everything, and the specification is in a different order to all my notes as we learnt it in a different order so everything seems a bit muddled!

Reply 616

parallal

Does anyone think we'll have questions on circulation?

Reply 617

oHellno

Original post by LifeIsGood

So at interphase it replicates, prophase contains the replicated DNA so when Anaphase takes place, it halves?

Yup

It's at anaphase when the two chromatids are pulled apart.

Reply 618

TlanTlan

Memorise the images of them too as you will get asked on those most likely.

Reply 619

ksimmi25

Show the results of density gradient centrifugation for 3 replications of E.coli beginning with 14N and then transferred to 15N and the opposite way round.

Can someone explain how to do this - i really don't understand 14N and 15N :/ apart from the fact that 14N is lighter.