AQA A2 Biology BIOL5 - 17th June 2015

Reply 600

maiisiie_08

4

Original post by sn4kebiteheart

Can someone please help me with genetic fingerprinting?!

thank you

What bit do you need help with? :smile:

Reply 601

sn4kebiteheart

2

Original post by maiisiie_08

What bit do you need help with? :smile:

All of it!?!?!?

I missed the lessons and panicking eeeeek

Reply 602

MollyMcFly1

13

Original post by sn4kebiteheart

Can someone please help me with genetic fingerprinting?!

thank you

This is what I've learnt:

Stages for fingerprinting..

1. Isolation of DNA. May make larger sample using PCR

2. Digestion. Produce fragments using restriction enzymes.

3. Separation. Separate fragments using electrophoresis. Soak in alkali to split DNA into single strands and use southern blotting to transfer to nylon membrane.

4. Hybridisation. Add radioactively labelled DNA probes, which bind to specific complementary base sequences

5. Development - use x-rays to see where the probes have bound. Creates a fingerprint.

Hope this helps :smile:

Reply 603

maiisiie_08

4

Original post by sn4kebiteheart

All of it!?!?!?

I missed the lessons and panicking eeeeek

Okay so genetic fingerprinting involves the use of DNA to identify how closely two samples (or two people) are related.

DNA contains introns, which don't code for proteins in an organism. Introns contain core sequences, which are repetitive sequences which are unique for each individual - apart from twins. Because of this, introns and core sequences are used in generic fingerprinting.

Extraction - DNA is taken from the sample, and it's quantity increased using PCR.

Digestion - restriction endonuclease cuts the DNA into fragments (cuts close to the core sequences).

Separation - gel electophesis separates the fragments and Southern blotting transfers the fragments into a nylon membrane. An alkali is applied to the gel to split double strands into single strands, a nylon membrane and absorbent paper is laid over the gel, which draws up the DNA fragments in the same position as on the gel. UV light fixes the fragments in place.

Hybridisation - labeled probes bind to the core sequences due to their complementary bases.

Development - an X-Ray film or observing the membrane exposes the probes (which are bound to the fragments of DNA), highlighting a series of bands. This is the DNA fingerprint.

Printing can be used in forensics, as suspect DNA and sample DNA fingerprints can be compared for similarities in the band positions.
For paternity tests, the childs fingerprint should have bands which correspond to either the mother or father's fingerprint, as half their core sequences are from the father and half from the mother.

Reply 604

Bethany_

2

On the June 2013 paper Q8c the question says, 'TO make the DNA probe, the geneticist had to find the base sequence of the normal gene. Once he had copies of the gene, what methods would he use to find the base sequence of the gene?

The mark scheme says
1. Restriction mapping/described
2. DNA/base sequencing (of fragments)/ description/name of method.

Now does that mean to get the two marks you literally need to write 'Restriction mapping and base sequencing of fragments' or you need to describe the methods?

If any one has a brief description of each method I would be very grateful too! Thank you

Reply 605

maiisiie_08

4

Original post by Bethany_

On the June 2013 paper Q8c the question says, 'TO make the DNA probe, the geneticist had to find the base sequence of the normal gene. Once he had copies of the gene, what methods would he use to find the base sequence of the gene?

The mark scheme says
1. Restriction mapping/described
2. DNA/base sequencing (of fragments)/ description/name of method.

Now does that mean to get the two marks you literally need to write 'Restriction mapping and base sequencing of fragments' or you need to describe the methods?

If any one has a brief description of each method I would be very grateful too! Thank you

I think as its only 2 marks you just have to say restriction mapping of the sequenced DNA fragments.

So DNA sequencing is the use of the Sanger method - using four test tubes which each contain a different terminator base, nucleotide bases, primers, DNA polymerase and the required DNA fragment. As binding in each tube is random, the double strands produced will be of varied length. Gel electophesis has split the fragments according to length - a voltage is applied across the gel so smaller fragments move further.

In restriction mapping, restriction endonuclease cut the DNA and the fragments are separated through gel electrophoresis. The distance between recognition sites for each endonuclease can be determined through the distance between each fragment, and so the sequence of each fragment can be determined.

Reply 606

quirksy

1

For the essay, roughly how many points should we be aiming to make? In the markschemes there are normally 15-20ish points so should we aiming to get around 10 of them, or more?

Reply 607

Bethany_

2

Original post by maiisiie_08

I think as its only 2 marks you just have to say restriction mapping of the sequenced DNA fragments.

So DNA sequencing is the use of the Sanger method - using four test tubes which each contain a different terminator base, nucleotide bases, primers, DNA polymerase and the required DNA fragment. As binding in each tube is random, the double strands produced will be of varied length. Gel electophesis has split the fragments according to length - a voltage is applied across the gel so smaller fragments move further.

In restriction mapping, restriction endonuclease cut the DNA and the fragments are separated through gel electrophoresis. The distance between recognition sites for each endonuclease can be determined through the distance between each fragment, and so the sequence of each fragment can be determined.

Thank you so much!!! I just want all the exams to finally finish now aha :angry:

Reply 608

joez009

1

Does anyone have any example essays with marks? Would be super helpful to see how much/scientific level is expected to get a decent mark. Much thanks.

Reply 609

EmilyC96

3

Does someone mind explaining q2b in June 2012 as I measured the sarcomere as 43mm but I can't get the right answer :/

Posted from TSR Mobile

Reply 610

nualamurphy5

1

Original post by quirksy

For the essay, roughly how many points should we be aiming to make? In the markschemes there are normally 15-20ish points so should we aiming to get around 10 of them, or more?

i think 4 detailed pointa would be enough

Reply 611

jennylisguan

hey!! how many essay plans are people making i have 23 plans but i don't know if i should do some more ?

Reply 612

djhodnett

9

Original post by jennylisguan

hey!! how many essay plans are people making i have 23 plans but i don't know if i should do some more ?

not doing any, its not difficult to write an essay as long as you spend 5 mins on a plan and cover most topics.

Reply 613

jf1994

15

Original post by nualamurphy5

i think 4 detailed pointa would be enough

Just 4?! I was expecting to have to write at least 10 or something silly like that...

Reply 614

MrPolish

2

Original post by Loveart99

Wow these are so so good! Thank you! Do you by any chance have notes on BIOL 1-4 as well?

sorry for the late reply, and sure:

Unit 1:
https://a9c4db5728f476f10dab258f06236e7e09aba195.googledrive.com/host/0B1ZiqBksUHNYUmM4NmpzWUItTjg/Key%20Points%20-%20Unit%201%20AQA%20Biology%20A-Level.pdf

Unit 2:
https://6e169229cd1764777398d0b4338ac5dbb77c600e.googledrive.com/host/0B1ZiqBksUHNYZ1dqZm10YldibVk/Key%20Points%20-%20Unit%202%20AQA%20Biology%20A-Level.pdf

Unit 4:
https://2473572087c0668999d962f6994e05e746d68d5b.googledrive.com/host/0B1ZiqBksUHNYUHRVM0twWUJxRUU/Key%20Points%20-%20Unit%204%20AQA%20Biology%20A-Level.pdf

:smile:

Reply 615

TheRaspberry

9

Is it true for the essay you could just write about anything within the syllabus (nothing to do with the question) and still get a potential 22/25?

Apparently this is because you would only lose the 3 relevance marks...

Reply 616

xoxxxoooxo

Some Unit 5 stuff
http://vbio.weebly.com/aqa-unit-5-revision-pack.html
And some essay plans.
http://grobybio.weebly.com/uploads/2/6/2/3/26235017/synoptic-essay-pack.pdf
:smile:

Reply 617

blu123

Anyone got any top tips for answering the essays? / how to prepare for them? at the minute im finding myself just focussing on the content for the questions, and hopefully just wing the essays, is this a bad idea?

Reply 618

jennylisguan

Original post by blu123

Anyone got any top tips for answering the essays? / how to prepare for them? at the minute im finding myself just focussing on the content for the questions, and hopefully just wing the essays, is this a bad idea?

depends if you know your content you'll be sorted for essay but the essays can be really specific and in the heat of an exam you might panic make a few plans id say