A2 Biology OCR June 2015 Revision Thread

if you want to sequence a gene then you have to

My teacher never mentioned any of that stuff ;_;

What's the point of separating DNA of the same length before amplifying it? When you talk about electrophoresis, you have to talk about how it separates DNA by length. How do we get our different lengths? Interrupted PCR. It's safer putting it in order.

I get what you mean. But one could argue, as it does say it in the book, that fragments cut before sequencing can also be put in size order as it can help to then sequence the fragments from the smallest to the largest fragment (maybe so they sequence fragments in a some form of order). Maybe it's a mistake in the book but I will make sure I put electrophoresis after the sequencing as well.

What didn't they mention? There are perks with having a Biology teacher who studied Genetics :')

Edit: You have a mixture of both types of nucleotide bases, the normal ones and the marked terminator ones. You get varied lengths of DNA because the terminator A C G U nucleotides can form H bonds with any of their complementary bases. So you could get one where you have a long strand of normal nucleotide bases, and then the terminator, or another with a shorter strand of nucleotide bases and a terminator. The first strand will be longer than the second.

*print screen*

Why would an uracil nucleotide be there? So just to clarify, the shorter fragments will travel faster? Then what's stopping the anti-sense strand mucking things up?

Ah ignore me, that's supposed to be thymine. It's definitely late :') the shorter fragments will travel faster. They never state anything about that you know, that's always been confusing tbh

Well, I don't know about you but I can only productively revise at night.

I've noticed a couple of facts that don't quite add up in our course and my teachers can't quite answer me either, like why is mRNA single stranged and why no RNA nucleotides casually bind to the bases and whatnot. It seems unlikely that an mRNA molecule to whisk through the nucleus and cytoplasm without anything binding onto it but hey, I guess that's what uni would be for

I'm usually a night owl too actually, but I refuse to revise on my birthday~
Exactly, they leave so much out. So many things that we should know about that aren't syllabus points. It's crazy.

Well, I don't know about you but I can only productively revise at night.

I've noticed a couple of facts that don't quite add up in our course and my teachers can't quite answer me either, like why is mRNA single stranged and why no RNA nucleotides casually bind to the bases and whatnot. It seems unlikely that an mRNA molecule to whisk through the nucleus and cytoplasm without anything binding onto it but hey, I guess that's what uni would be for

RNA is at risk of binding to other stuff (nucleotides etc) I think (possibly am wrong) that it doesn't because a single strand RNA molecule can fold up on itself and form base pairs with other regions of itself. This leads to the RNA having a very specific three dimensional structure which is important for its functioning.

You mean like the tRNA structure? And would it be too much to ask how/what breaks the bonds apart when required for translation?

Could someone explain to me where PCR plays a role in sequencing the genome?
I have memorised the steps for sequencing the genome using BACs and the automated process, but I can't really see where does PCR come into either. I mean, I know the automated is based on PCR, but how?
For the BAC method, in the OCR book it says as the cells grow many copies of the DNA strands are produced and cells containing specific BACs are taken; so is PCR even needed for this method?

Any help would be much appreciated.

You can use interrupted PCR to sequence DNA. This a is where the last bases added is fluorescent and each piece is a different length, meaning a computer can tell you the sequence when you put it in after you separate the different length by electrophoresis

Posted from TSR Mobile

You can use interrupted PCR to sequence DNA. This a is where the last bases added is fluorescent and each piece is a different length, meaning a computer can tell you the sequence when you put it in after you separate the different length by electrophoresis

Posted from TSR Mobile

Hey guys, I posted something similar like this a few days ago if you remember, but since then i've just had a flick through the whole of f215 and i really hardly know any of it And i'm freaking out I thought i would know a decent amount of f215, as i know most of f214 well, but i don't.

Like i said before i still I have to cover the last 2 modules myself, which god willing ill finish by the end of next wk (I've only started the ecosystems module but it seems ok). Now if i can go over most of f215 and memorize most of it before the exams start in June, without doing past papers for f215, do think i could get a low A (or a v.high B like a few UMS away from an A) for f215? Btw I haven't really had any tests/mocks for f215.

Not joking, i feel like im going to fail my exams (btw I need AAB). Please, somebody give me some gd news.

have you done a f325 paper?

Hey guys, I posted something similar like this a few days ago if you remember, but since then i've just had a flick through the whole of f215 and i really hardly know any of it And i'm freaking out I thought i would know a decent amount of f215, as i know most of f214 well, but i don't.

Like i said before i still I have to cover the last 2 modules myself, which god willing ill finish by the end of next wk (I've only started the ecosystems module but it seems ok). Now if i can go over most of f215 and memorize most of it before the exams start in June, without doing past papers for f215, do think i could get a low A (or a v.high B like a few UMS away from an A) for f215? Btw I haven't really had any tests/mocks for f215.

Not joking, i feel like im going to fail my exams (btw I need AAB). Please, somebody give me some gd news.

have you done a f325 paper?