AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

has anyone the 4bi and 4dii on p.g 235? For the first one the mark scheme says that G binds to G! How is the possible? Also I don't understand how it is valine in 4bii

Also q4bii on p.g 245, the last sentence of mark scheme says that transcription is prevented when mRNA is broken down. Isn't it meant to be translation???

It would be great if someone could explain this to me.

*Subscribes*

We've nearly finished, we did the course in a weird order though and have some stuff on neurones and muscle contraction left. We haven't done many of the synoptic essays yet.
I still haven't taken the biology unit 4 exam either (my college is annoying and insists we must take both exams in june...More stress!)

We did those questions in class- there are a few typos in the book, it's not just you!

On pg 235 qn 4, you'll notice the 2 codes for valine are the same. One should be GUU. On the mrna diagram at the top, the first triplet is GCA not GGA.

Hope this helps

I was going to create a thread on this.
I think it'll be a good place to post any essay questions you've been given so we can all have a go at some.
I might also post my essay plans at some point too.

To be honest, I need the support from you guys! I have 2 of the worst teachers ever, seriously we do not learn a thing. Everyone has had to get tutors but I might not be able to afford one :|
I found out today we have only covered 3/8 topics! We have 3 weeks left and we haven't even done any practice essay or preparation!
So yes, I am starting to panic.

I have a question for you guys, for the essay question how much knowledge do we need to know on the AS content? Does it have to be detailed, because I have a memory like a sieve.

It would be silly to have to learn everything again and they don't expect you to. But they do expect us to know the major topics that have been popping up over the course such as enzymes, proteins, DNA, ATP and so on. I thought of grouping all the sub - topics together over the whole of AS and A2 and refer to it when writing essays. After a while I should be able to do it without it.

Also cover the content ASAP because it's huge and it takes time to digest it all, as long as you practice essays now there won't be an issue.

Ooh, ok thanks a lot!
I think I'll just read through the revision manuals and anything that seems to occur quite often or tie in with other sections I'll probably make detailed notes of. I think enzymes has cropped up so much now that the information is permanently embedded in my brain...

For the essays... do you think it's better to cover fewer topics going into detail, or to cover quite a few topics but just make a few statements and not go into such detail?

I'm worrying now, especially as my teachers have only covered just over half the content and we only have 1 week of school left!

Also I thought of researching some things for each chapter that we have done over the entire course and if it works out I can write about it in the essay... that's what could get us the 14/16 marks.

I reckon about 4/5 major topics from AS & A2 and trying to squeeze in minor topics if possible, otherwise it would look we are rambling about everything and anything. They expect us to talk about the main things that we have covered to this level, that's what it says in the markscheme (something like that).

As for the content, which chapters have you done so far? I would urge you to do chapter 10 and 16, especially chapter 16 as it's the hardest! Then you can ask your teacher if you don't get it. Chapter 9 is okay, 10 is hard but easy once you understand it, 11 is a lot of memory work, 12 is okay, 13 is quite easy, 14 is easy, 15 is easy and 16 is the hardest one! (Using the Nelson Thornes book btw)

Just know that it is still not too late! Prioritise biology.

It gives me nightmares!

Ive got a question about
Gene sequencing
Its well explained in CGP but I only am a bit confused about the differences between electrophoresis on its own and in the Gene sequencing!!

I mean , in gene sequencing bands are nucleotides whereas in fingerprinting bands are DNA fragments!!

ANyone shed some light please.

Yeah I worked it out. Thanks for your help though, was really pissed before

How is your prepration going?

Both involve DNA fragments. With gene sequencing, you use the Sanger method, which is where you have 'terminator nucleotides' which attach to the complementary nucleotide of the DNA strand. This stops anymore nucleotides being attached, so you end up with chunks of DNA.

DNA fingerprinting also makes DNA fragments, but it uses restriction endonucleases. If you remember from the stuff on in vivo gene cloning, restriction endonucleases cut at a specific recognition site on the DNA strand. So by using this, forensic investigators can compare two samples of DNA from the fingerprint they produce. If the DNA they find at the crime scene is the same as one of their suspects, then the restriction endonuclease will cut at the same point and produce the same fragments.

Hey

Could you please explain that which sequence we determine through Sanger method (terminator nucleotides) and gel electrophoresis. Is it the sequence complementary to template DNA or is it the actual sequence of template DNA? My teacher did not explain it clearly

And yeah the last thing you want to heppen is learn wrong info from errors in the book.

Thanks again

Both involve DNA fragments. With gene sequencing, you use the Sanger method, which is where you have 'terminator nucleotides' which attach to the complementary nucleotide of the DNA strand. This stops anymore nucleotides being attached, so you end up with chunks of DNA.

DNA fingerprinting also makes DNA fragments, but it uses restriction endonucleases. If you remember from the stuff on in vivo gene cloning, restriction endonucleases cut at a specific recognition site on the DNA strand. So by using this, forensic investigators can compare two samples of DNA from the fingerprint they produce. If the DNA they find at the crime scene is the same as one of their suspects, then the restriction endonuclease will cut at the same point and produce the same fragments.

In the Sanger method they first split the DNA double helix into two single strands, and then the primer binds with its complementary strand. Then the free nucleotides are added on using DNA polymerase, until a terminator nucleotide attaches and stops anymore nucleotides being added.

Im doing AQA and there is no Sanger method! Weve got chain termination method

instead..dunno if theyre the same ohh description is the same tho ...

CGP just doesnt make any sense to me atm..
Here is CGP example : There is a image of electrophoresis in gene sequencing , in which there is a T nucleotide (Not fragment!!?) at the bottom of the gel near +ve electrode

Thanks for reply