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AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

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Reply 2000

Hi could soon clear something up for me, in DNA sequencing, each test tube has DNA fragment + modified nucleotide + bank of nucleotides + radiotactive primer+ DNA polymerase.

Surely the fact that the primer will have to attach to some bases at the beginning of the fragment means that when you read off the sequence on the electrophoresis gel you'll be reading from the last nucleotide on the primer - not the beginning of the DNA fragment?

Reply 2001

Jeshiii

Original post by Aiboz

Well how I remember is it that we have two ways - increase of a heartbeat and slowing of a heartbeat.

So when we exercise there is an increase in metabolic/muscular activity, this increases the rate of respiration and thereby increase the level of carbon dioxide in the blood. When carbon dioxide is dissolved in solution it becomes acidic. So this increased level of carbon dioxide lowers the pH level. The chemoreceptors in the walls of the carotid arteries (the arteries that serve the brain) detect this and send signals to the medualla oblongata in the brain. The centre in the medulla oblongata that increases heart rate increases the frequency of impulses to the sinoatrial node via the sympathetic system. The sinoatrial node increases the heart beat. This causes increased blood flow, which removes the carbon dioxide from the lungs faster. This means carbon dioxide levels decrease back to normal.

If this helps, quote me. I will then explain the control in slowing down the heartbeat and pressure receptors.

Thankssss! That was soo much help :smile:

I think i'll just end up forgetting the proper words, like sympathetic and parasympathetic. Do we have to know the proper channels and stuff it goes down?

Reply 2002

Ineluctable

Original post by blackberryaddict

Unit 5 can't be taken in January so the only papers are the specimen and June 2010. June 2010 grade boundaries:

A* 69
A 62
B 55
C 49
D 43
E 37

That made me feel better, those aren't too bad

Reply 2003

strawberry_cake

Think oestrous cycle will come up again? :frown:

Reply 2004

sarahlovesleon

Original post by blackberryaddict

Unit 5 can't be taken in January so the only papers are the specimen and June 2010. June 2010 grade boundaries:

A* 69
A 62
B 55
C 49
D 43
E 37

wow and its out of 100 isn't it? if you try and get like 20 on the essay, you could do pretty badly in the questions but still get a pretty good grade!

Reply 2005

Tericon

Original post by sarahlovesleon

wow and its out of 100 isn't it? if you try and get like 20 on the essay, you could do pretty badly in the questions but still get a pretty good grade!

But that is just one paper, which people found difficult, the examiners report is full of 'a poorly answered question' and such phrases.

This one may have higher grade boundaries, it all depends on how well prepared people are and how the questions are worded.

Reply 2006

cheekymon999

Original post by johnsoloman

Hey, is anyone bothering to learn AS biology or at least go over it for the synoptic essay tomorrow?
I'm not sure whether I should or not, as i haven't got much time left

its too much information so i dont think ill bother :/ at least if you focus on this topic you can do well on the questions and then at least write about A level stuff in the essay - and if you remember AS stuff - its a bonus

Reply 2007

mkb230

Original post by Tericon

Your diagram is fantastic, but I'm still a little confused...

I get that 2 must be nearest the label as its the radioactive fragment, but its the partial digests that confuse me, they add up to more than 10? How can this be?

How to find the fragment nearest the radioactive label is pretty much the only bit of RM i get :tongue:

Original post by blackberryaddict

Unit 5 can't be taken in January so the only papers are the specimen and June 2010. June 2010 grade boundaries:

A* 69
A 62
B 55
C 49
D 43
E 37

Thanks a lot ! Grade boundaries look significantly higher compared to Unit 4 even though this unit is a lot harder. So does that mean that people can't re sit this exam in January?

Reply 2008

blackberryaddict

Original post by sarahlovesleon

wow and its out of 100 isn't it? if you try and get like 20 on the essay, you could do pretty badly in the questions but still get a pretty good grade!

Yeah out of 100. Haha getting 20 on the essay is easier said than done though. And I think the bit people haven't really prepared for. What the essay topic is will make or break me. Oh god the pressure with Uni offer :frown:

Reply 2009

arvin_infinity

Someone tell me what I need to know from As since Ive almost forgotten the entire As

+rep

Also which legacy paper is more similar

Reply 2010

Stirlo

Original post by mkb230

Thanks a lot ! Grade boundaries look significantly higher compared to Unit 4 even though this unit is a lot harder. So does that mean that people can't re sit this exam in January?

No you have to wait for the summer

Reply 2011

Boo!xx

Original post by Jin3011

The bases on the mutated gene are determines by DNA sequencing and stored in genetic libraries.
A fragment of DNA that has bases complementary to the mutated portion of the gene is produced.
The DNA fragment is radioactively labelled to produce a DNA probe (or the nucleotides are radioactively labelled to be more accurate)
And PCR is used to produce many compies of this DNA probe using radioactive nuclotides rather than normal ones.

After you've used the single stranded DNA to a make the double strand in PCR do you use DNA helicase to seperate them, or just heat?

Also how do you locate which gene is mutated?

Reply 2012

mkb230

Oh and good luck to everyone tomorrow :smile:

I have got D1 at 9:30 and then this one straight afterwards. Biol and Chem 5 will probably decide my future :angry:

Reply 2013

flowerscat

Original post by TheUsername42

From the bottom up-
A band corresponding to primer only - this is discounted (and you won't be shown this band in the exams)
The first band of your sequence will correspond to (Primer)+(one base)
The second of your sequence will correspond to (Primer)+(two bases)
The third band of your sequence will correspond to (Primer)+(three bases)

is that any more clearer?

Original post by kingsmod1

sorri guys but i do not understand why they use the sanger method and how that helps locate the bases they are lookin got, i mean if they didnt kno the bases they lookin for so then why are primers complemantary to it

many thanks!!!! :P

Reply 2014

angel1992

Original post by moniquesungirl

Anyone fancies to do a recap of chapter 16? For me is the hardest one :/

ok so where to start right
two ways to make dna fragments

reverse transcriptase- is an enzyme converting mrna into dna
useful because introns so can be used to transform bacteria only, which can then produce the proetins( bacteria cant slice)

restriction endonucleases- these are made by bacteria to cut up viral dna
they cut at recogntion sites which ususally have palindromic sequences
sticky ends are produced because of the bases being revealed, and they are better than blunt ends as they are more specific
restriction endonucleases can be used in vivo cloning to cut out a gene ( which has these recognition sites either side) and stuck into a plasmid cut once using the same restriction endonuclease

these plasmids can used as vectors to insert into host cells
note that if you want to transform a bacteria you usually use reverse transcriptase as well as restriction endonuclease but if you want to transform an animal or a plant you dont have to use reverse trancriptase becuase these organsims can splice out introns

in vivo gene cloning clones directly and isnt done in living cells, you cant transform organisms in this way, as organisms are transformed through vivo cloning as the recombinant dna is replicated as part of their development

in vitro is better as more dna is made in a shorter space of time, and also it doesnt need living cells so reduceds the need for growth mediums and culturing etc, but as its less specific it means that contaminant dna is also amplified,in addtion its less accurate because gene cloning for example conducts less errors, as its in living tissue so although mutations occur they are rare, while in vitro clonning isnt in lving tissue and so its artificial dna cloning and more errors are made

gene therapy can treat cystic fibrosis as well as scid, by the use of adeno viruses, retrovirsues, or liposomes, and could either use somatic cell therapy or germ line therapy where germ line is negative because of the use of fertilised eggs and manipulating them , while its positive as it prevents immune reponses and is longer lived in that repeated treatement arent needed and isnt passed on to future regenerations. aduly Stem cells can also be used here, in somatic cell therapy, as they prevent repeated treatments being needed but it doesnt eliminate the fact that it is passed onto future geneartions..

sequencing a gene
sanger method/chain termination method
restriction mapping- which aids sequencing as enables larger genes to be sequenced

locating a gene- this is done after the sequencing method- using dna probes

genetic screening and genetic fingerprinting both use dna probes
in genetic screeing probes used to locate genes, in genetic fingerprinting porbes used to locate core sequences in introns which are at the same locations in all individuals but the number of times their repeated varies in each individual

below is just a summary of where each of the different features are in different processes

primers-
pcr
sanger method

dna probes
genetic fingerprinting
restriction mapping
locating a gene

pcr
genetic fingerprinting
sanger method
genetic scrreening- te replicate the probe
in vitro cloning- it is invitro clongin

hybridisation
locating genes- dna probes
genetic fingerprintin- dna probes

restriction endonucleases-
restriction mapping
in viv gene cloning
genetic fingerprintin
used in gene therapy to cut out the gene etc and insert it as a vector-

gel electrophoresis-
dna fingerprining
sequencing dna
restrcion mapping
locating a gene uv /xray

Reply 2015

Jin3011

Original post by Boo!xx

After you've used the single stranded DNA to a make the double strand in PCR do you use DNA helicase to seperate them, or just heat?

Also how do you locate which gene is mutated?

Probably heat, but I'm not sure.

The location of the mutated gene is determined by the annealing of radioactive probes which can be seen by exposure of X ray film.

Reply 2016

Tericon

Can someone please help me with 10ci and ii? I know the answer, but don't understand how graph shows this? And what on earth does 'heat-killed' mean?

http://store.aqa.org.uk/qual/gce/pdf/AQA-BIOL5-W-SQP-07.PDF QP

http://store.aqa.org.uk/qual/gce/pdf/AQA-BIOL5-W-SMS-07.PDF MS

Reply 2017

angel1992

can anyone explain the difference between endotherms and ectotherms in terms of their activity and body temperature- can you relate it to metabolism etc??