AQA BIOL5 ~ 17th June 2013 ~ A2 Biology

You should be able to see this if you put it on word and zoom in... if not, message me and I can email you it or pictures of different parts

Hi has anybody got the AQA Jan 13 unit5 Biol past paper! ran out of papers to revise from and this s the only one i cant get my hands on

Hi has anybody got the AQA Jan 13 unit5 Biol past paper! ran out of papers to revise from and this s the only one i cant get my hands on

really struggling with chapter 16.

spec says fragments are produced by:
A) using reverse transcriptase (I understand this)
B) Using restriction endonucleases (Sort of understand this, how will cutting up the DNA help isolate the fragments? Also does the body have enzymes to cut at recognition sites of every single gene? Finally, since restriction endonucleases cut at palindromic sequences, what if the required gene doesnt contain palindromic sequences?)
C) PCR (confused because the NT book says this is a method for cloning AFTER fragment has been collected whereas the spec says it is for collecting fragments)
In other words, is PCR a way of collecting the fragments, cloning the fragments or both?

Next part I dont understand is if the fragments are obtained using reverse transcriptase, then how will they be inserted into plasmid and cloned in vivo?
since no restriction enzymes were used for obtaining the DNA, which restriction enzyme will be used for cutting the plasmid.
(I think if DNA fragments are obtained from reverse transcriptase, then in vitro is the only method of cloning. Is this correct?)
Only other possible explanation is that even if the DNA fragment is obtained from reverse transcriptase, it is still cut by a restriction enzyme which is also used to cut the plasmid and then inserted into bacteria. This doesnt seem correct though.

AS you can see from this post, im really struggling. If anyone can help me with chapter 16 or anything discussed in this post, I will really appreciate it. Fully understand all the other chapters now so maybe I will be able to return the favour sometime

Yes

During DNA replication DNA Polymerase synthesizes the strand whilst DNA Ligase completes it. The bit I think a lot of people don't realise is that Polymerase does not always start at the beginning of the DNA strand and move down the DNA sequentially. Polymerases bind at different points in the single strand of DNA indicated to them by primers. Sometimes Polymerases start in the middle of the section and attach a few nucleotides before falling off. When the DNA is replicated in the cell cycle many Polymerases will bind to the same strand to simultaneously replicate the DNA.

During replication there are many different sections of replicated DNA on the strand (the sections are called Okazaki fragments). Once the DNA Polymerases have fallen off DNA Ligase travels along the DNA and fills in any gaps between the different sections the Polymerases completed. This means that many Polymerases can replicate the DNA at once, which makes replication much faster overall.

In unit 5 we learn that DNA Ligases are also used in Biotechnology to join two sections of DNA that had been separated (using restriction endonucleases) back together again. Here it does the same thing (forms covalent phosphodiester bonds between the two fragments).

Hope this helps

really struggling with chapter 16.

spec says fragments are produced by:
A) using reverse transcriptase (I understand this)
B) Using restriction endonucleases (Sort of understand this, how will cutting up the DNA help isolate the fragments? Also does the body have enzymes to cut at recognition sites of every single gene? Finally, since restriction endonucleases cut at palindromic sequences, what if the required gene doesnt contain palindromic sequences?)
C) PCR (confused because the NT book says this is a method for cloning AFTER fragment has been collected whereas the spec says it is for collecting fragments)
In other words, is PCR a way of collecting the fragments, cloning the fragments or both?

Next part I dont understand is if the fragments are obtained using reverse transcriptase, then how will they be inserted into plasmid and cloned in vivo?
since no restriction enzymes were used for obtaining the DNA, which restriction enzyme will be used for cutting the plasmid.
(I think if DNA fragments are obtained from reverse transcriptase, then in vitro is the only method of cloning. Is this correct?)
Only other possible explanation is that even if the DNA fragment is obtained from reverse transcriptase, it is still cut by a restriction enzyme which is also used to cut the plasmid and then inserted into bacteria. This doesnt seem correct though.

AS you can see from this post, im really struggling. If anyone can help me with chapter 16 or anything discussed in this post, I will really appreciate it. Fully understand all the other chapters now so maybe I will be able to return the favour sometime

B) By cutting out the gene, you're separating it from the rest of the DNA strand, hence 'isolating' it from the rest. All this part is done outside the body, the 'in vivo' bit refers to the gene being cloned in living cells i.e. the host cells. The majority of the DNA tech section is all done in a lab Then I assume they can't cut it? You don't really need to know that, don't worry, just assume the sequence is palindromic
C) From my book 'PCR is a method of copying fragments of DNA'

The plasmid is cut using the same Restriction endonuclease, so will have complementary sticky ends to the gene
DNA is cut with reverse transcriptase.

Hope that helps Do you not have the AQA endorsed textbook, that's what I use and it's easier to understand in the way it's set out

What joins the new chain with all its phosphodiester bonds to the existing chain then? By that I mean the hydrogen bonds between the bases? This is confusing as in many of the A level books, they say that DNA polymerase does this, but clearly it doesn't!

Hydrogen bonds reform themselves, they don't need any enzymes to join the base pairs.

You do realise the question you asked before will not be asked in the exams!

Unless of course, you are preparing for the synoptic essay

I don't think you've answered the question! Also where its in bold you put reverse transcriptase, when you meant restriction endonuclease, which I've changed it to. The original poster meant what if restriction endonucleases are not used to obtain the DNA fragment, so you cant use the same ones to cut the plasmid?

My teacher tends to talk a load of rubbish, but he seemed to be under the impression that a list of possible essays is posted each year and that the essays in the paper will be on it, plus a few others. Anyone know if this is true?

My teacher tends to talk a load of rubbish, but he seemed to be under the impression that a list of possible essays is posted each year and that the essays in the paper will be on it, plus a few others. Anyone know if this is true?

I don't think so, I'm fairly sure my teacher would have said so otherwise.

However, sometimes people make predictions and that topic may coincidentally come up. That's happened in some of my exams before, but I don't think there's an official list of essay questions. Would be too easy to learn an essay plan off by heart otherwise :/