F215 - Revision thread 13th June 2011

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chromosomes basically have their own centromere whereas chromatids share a centromere, the centromere is the bit they are pulled apart by in mitosis, chromatids are usually identical to each otyher as they are the result of dna replication in interpahase however in interkinesis(the bit before meiosis 2) the dna does not replicate so the two sister chromatids that split and become chromosomes in their own right are not genetcally identical
hope this clears up any confusion :smile:

thanks mate how did u do in the january exam ?

Reply 61

J DOT A

How far have you guys gotten? I am on Growth curve....

Reply 62

rebmu

Original post by biology12345

thanks mate how did u do in the january exam ?

did better than last year lol scraped an a in f214

Reply 63

biology12345

Original post by rebmu

did better than last year lol scraped an a in f214

yh same got the 72/90 on the boundry for an a mine wernt a resit or aything though

Reply 64

kabolin

looking for some ****ing past papers cant find any. the relevant q's r jumbled up. past paper bank is **** can some1 plz find relevant past papers

Reply 65

hannahnguyen

why there are so many things to rmb in unit 5 :frown:

unit 5 is like the most difficult unit ever :frown:

Reply 66

rebmu

Original post by biology12345

yh same got the 72/90 on the boundry for an a mine wernt a resit or aything though

nah wasn't a resit was live but just wasn't expecting it (even though i worked my ass off)
as got a d in both as units (resitting them this summmer so hopefully all will go well)

Reply 67

sportycricketer

Original post by hannahnguyen

why there are so many things to rmb in unit 5 :frown:

unit 5 is like the most difficult unit ever :frown:

Yeah agreed! It's just memorising the work imo. But also they word the questions in such a weird way :s-smilie:

. If it was straight memorising it wont be THAT difficult

Reply 68

infernalcradle

just to say.,....we haven't even finished a third of the syllabus......and the bit we have covered....we barely know....

so my class will probably be bringing down those boundaries :biggrin:

Reply 69

sportycricketer

Original post by infernalcradle

just to say.,....we haven't even finished a third of the syllabus......and the bit we have covered....we barely know....

so my class will probably be bringing down those boundaries :biggrin:

but considering you have a medic offer, amongst with other people and other good offers (like me :P) you'll probably do the hard work and cover it yourself and ace it haha :biggrin:

Reply 70

infernalcradle

Original post by sportycricketer

but considering you have a medic offer, amongst with other people and other good offers (like me :P) you'll probably do the hard work and cover it yourself and ace it haha :biggrin:

hmm....ace it?? :rolleyes:

but yes, I intend to become "ill" next week, so regrettably, I won't be able to go back to school.....

I will however, make miraculous 1 day recoveries on the days which I have exams :biggrin:

Reply 71

sportycricketer

Original post by infernalcradle

hmm....ace it?? :rolleyes:

but yes, I intend to become "ill" next week, so regrettably, I won't be able to go back to school.....

I will however, make miraculous 1 day recoveries on the days which I have exams :biggrin:

How are you actually revising for it? :/ I really hate memorising all of it. I managed to finish my revision notes last week and doing past paper questions here and there :s-smilie:

Reply 72

J DOT A

How far have you guys got? I am just about completing module 2, and going onto ecosystems...

Reply 73

infernalcradle

Original post by sportycricketer

How are you actually revising for it? :/ I really hate memorising all of it. I managed to finish my revision notes last week and doing past paper questions here and there :s-smilie:

I have a trusty whiteboard.....

condense each double page onto the whiteboard....wipe it....write from memory.....

then do past papers......

this only works for bio and chem for me.....

Reply 74

larry000

Can someone help me understand the steps involved in sequencing a genome for an organism. I dont get it at all :frown:

Reply 75

slacker07906

I'm going to start tomorrow...I promise :P

Reply 76

sportycricketer

Original post by larry000

Can someone help me understand the steps involved in sequencing a genome for an organism. I dont get it at all :frown:

is it automatec sequencing you need help with??

Reply 77

Waqar Y

Original post by larry000

Can someone help me understand the steps involved in sequencing a genome for an organism. I dont get it at all :frown:

Allrighty, let's start with the first bit then:

First, you've gotta get the section of the genome you want - that is the gene you want from which part of the chromosome.
To do this you can, extract the part of the genome you want by breaking it off the chromosome, this is known as a shotgun approach.

Then, you've got a lot of genome present, so you put it into BAC (bacterial artificial chromosome) and you insert that BAC into E.coli

E.coli then reproduces, and you end up with loads of copies of the genome.

You then use restriction enzymes to cut it into fragments, this gives overlapping fragments because you've got loads of sections of the genome which have been cut at different places.

You then mix the fragment types with DNA polymerase and free DNA nucleotides and primers(which are short strands of DNA that bind to the 3' end of DNA)
AND ALSO Terminator bases, which have one of four colours (As there's only 4 possible bases A T C G)

The primer binds/anneals to the 3' End of DNA - this allows DNA polymerase to get working and adds the free nucleotides to the fragment.

So, when the terminator base is added and binds to the DNA fragment, it throws off the enzyme DNA polymerase, so DNA replication is stopped.

Therefore, different fragments will be thrown off at different points, and will have one of four colors ( A could be red, T could be green, C could be yellow and G could be black) - These are fluorescent labeled and you'll see why they're useful later on.

- So now you've got different fragment lengths of your genome, that has been stopped at different points for each fragment.

you then separate using electrophoresis, it involved cutting a well on a slab of agar, electric current is passed through the DNA fragments that you place in the well.
DNA is negatively charged cus of the phosphoryl groups, so it'll move to the positive end.

Shorter DNA fragments will pass through quicker through the gel, so you'll end up with fragments on this gel that are separated by size.

They'll pass through an automated sequencer at the end of the gel, and the flourcent label will be used by this automated sequencer to give the colour of that fragment, therefore the bases to.

Reply 78

infernalcradle

hmm.....do you think its worth not revising any the stuff that came up majorly in the jan exam as considering they focused on those aspects, it won't come up....or at least, not in anything more than a few marks