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AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

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Nobody seems to have discussed this question yet:

"...One way to tell whether or not the DNA has been completely digested is to count up the total length of the DNA fragments. Explain how scientists could use this data to conclude that the DNA has not been totally digested by the enzymes."

This completely threw me.

As I see it, either the total fragment length is equal to the length of the original DNA or it isn't.

If it is, this does not prove anything. No matter how many times you cut a piece of string, the total length of the fragments will stay the same. The total fragment length gives no indication whatsoever of whether or not there are restriction sites yet to be cut.

If it isn't, then bases have apparently vanished into thin air. Which cannot happen.

I have checked the textbook and the revision guide, and there isn't a single hint of the answer to this question. Possibly I just read it wrong.

Edit: The only way total fragment length would be of any use is if they knew how many fragments they would get to start with, in which case they don't even need to calculate total length, they would just need to count the fragments.
(edited 12 years ago)

Dude You totally made my day.
It says that I'd get 60 UMS
from my 37 raw marks in the ISA.
This is freaky. I was doing my calculations
using 37 as UMS LOOOOOOOOOOL
Reply 3142
Original post by Boo!xx
PCR!! Genius, wish I'd thought of it!

I wrote about:
nitrogen
carbon
water
menstraul
cardiac
calvin
cell cycle
bacterial divison




I also included the predator prey cycle as a similar question came up on the old spec and they wanted you to include an ecological cycle. But I'm sure with all those you included it won't make a difference
Original post by abbeyf
I also included the predator prey cycle as a similar question came up on the old spec and they wanted you to include an ecological cycle. But I'm sure with all those you included it won't make a difference


i also wrote about action potentials how they start and reset aswell as the synapse
Reply 3144
Can anyone get hold of a copy of the paper?
Original post by JeevesFTW
Nobody seems to have discussed this question yet:

"...One way to tell whether or not the DNA has been completely digested is to count up the total length of the DNA fragments. Explain how scientists could use this data to conclude that the DNA has not been totally digested by the enzymes."

This completely threw me.

As I see it, either the total fragment length is equal to the length of the original DNA or it isn't.

If it is, this does not prove anything. No matter how many times you cut a piece of string, the total length of the fragments will stay the same. The total fragment length gives no indication whatsoever of whether or not there are restriction sites yet to be cut.

If it isn't, then bases have apparently vanished into thin air. Which cannot happen.

I have checked the textbook and the revision guide, and there isn't a single hint of the answer to this question. Possibly I just read it wrong.



If you have a sample of DNA that is all 6 units long.

You cut it correctly: 3 2 1 is what you end up with.

Put if you only get a partial digest. You'd end up with 5 1.

Because you're doing lots of digests, the DNA when electropherisised (is that a word), would spread out: 5 3 2 1. The sum of the partially digested DNA is greater than that of the original, thus it is partially digested.
Reply 3146
Original post by JeevesFTW
Nobody seems to have discussed this question yet:

"...One way to tell whether or not the DNA has been completely digested is to count up the total length of the DNA fragments. Explain how scientists could use this data to conclude that the DNA has not been totally digested by the enzymes."

This completely threw me.

As I see it, either the total fragment length is equal to the length of the original DNA or it isn't.

If it is, this does not prove anything. No matter how many times you cut a piece of string, the total length of the fragments will stay the same. The total fragment length gives no indication whatsoever of whether or not there are restriction sites yet to be cut.

If it isn't, then bases have apparently vanished into thin air. Which cannot happen.

I have checked the textbook and the revision guide, and there isn't a single hint of the answer to this question. Possibly I just read it wrong.


Agreed.

As a complete guess I said that if the DNA was not fully digested it would add up to more than the 'size' (whatever that means...) of the fragment or whatever.

WTF. What did you write?
Reply 3147
Original post by kingjohno
If you have a sample of DNA that is all 6 units long.

You cut it correctly: 3 2 1 is what you end up with.

Put if you only get a partial digest. You'd end up with 5 1.

Because you're doing lots of digests, the DNA when electropherisised (is that a word), would spread out: 5 3 2 1. The sum of the partially digested DNA is greater than that of the original, thus it is partially digested.


Hmm that's what I thought
Reply 3148
Original post by RodrigoB
Dude You totally made my day.
It says that I'd get 60 UMS
from my 37 raw marks in the ISA.
This is freaky. I was doing my calculations
using 37 as UMS LOOOOOOOOOOL


Hahah well you can add 23 UMS to that now!
Glad to help :top:
Reply 3149
I got 35 raw marks in BIO6 ISA :frown: what ums would I get?
Does anyone know what the UMS break down for A2 is? How much the total UMS is for Unit 4, 5 and the ISA?
Original post by kingjohno
If you have a sample of DNA that is all 6 units long.

You cut it correctly: 3 2 1 is what you end up with.

Put if you only get a partial digest. You'd end up with 5 1.

Because you're doing lots of digests, the DNA when electropherisised (is that a word), would spread out: 5 3 2 1. The sum of the partially digested DNA is greater than that of the original, thus it is partially digested.


GODDAMMIT THAT'S SO SIMPLE.

Still, only one which really stumped me. The rest seemed pretty straightforward.

Seriously kicking myself in the jewels right now for not thinking of that.
Original post by OriginOfShowbiz
Does anyone know what the UMS break down for A2 is? How much the total UMS is for Unit 4, 5 and the ISA?


there u go http://store.aqa.org.uk/qual/gce/pdf/AQA_W_2410_GS.PDF
Reply 3153
What was the answer to the question about how many cuts are made by the restriction endoneuclease. Was it 3 as it was a circular plasmid.

What did people get for the question on why the yield of the pupae grown from a seed will differ to each other.
Original post by fsaeed20
What was the answer to the question about how many cuts are made by the restriction endoneuclease. Was it 3 as it was a circular plasmid.

What did people get for the question on why the yield of the pupae grown from a seed will differ to each other.


I said two as there were two restriction sites.

The yields will differ because sexual reproduction (seeds) involves meiosis and random fusion of gametes, so they will be genetically different, hence different yields.
Reply 3156
Original post by wiggle-bacon
i also wrote about action potentials how they start and reset aswell as the synapse


Yeah I put that one in:
Carbon/nitrogen cycles
Predator-prey
Photosynthesis
Mitosis
Meiosis
DNA replication
Transpiration stream
And action potentials

I really hope I do well in the essay to save me because I know I did badly in the stupid fly question.
Original post by lou12
what did people write for the one about the iaa travelling on the shaded side. i cant remeber the question


Active transport, but not too sure! But I spoke to one of my teachers, and he said diffusion and active transport was possible, depending on where it happens.

What exactly was the question, does anyone remember?
Hey, I just wanted to see if anyone else had the same idea as me about the IAA with temperature and why the underside of the leaf has higher IAA with increasing temperature.

I put down that it allows the leaf to curl up and so there is less water vapour lost as the diffusion gradient of water decreases.
Reply 3159
Original post by xelaman
That was the second part of the qs-the first part was related to thier action once they reach the cell :frown:


oh crap. i think i must have missed the second part. i only remember writing about how they reach the cell. was there another question on how they effect the cell?

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