# Biology help watch

1. Hey, I know that's an awkward question but how do you delete a thread in here?
2. (Original post by AortaStudyMore)
If you're unsure then plot it on a graph, draw 2 bars representing the means, and then do mean + SD to represent the top of one bar and mean - SD to represent the bottom of the bar for each bar, and you'll see there is some quite major overlap!
What should i do when its like that in an exam like this?
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3. (Original post by Perfection Ace)
How much did you pay for medic school? Like, do you even have to pay or anything?
Everyone gets loans, so technically I'm not paying anything now, but I will have to pay the loan back when I (hopefully) get a job in the future
4. (Original post by dyezrawna)
What should i do when its like that in an exam like this?
I'm not sure what the problem is, you've done everything right, it is just a maths issue if you can't work out if the error bars overlap from the numbers. I mean, a way you can work it out quickly is by looking to see whether the upper limit of one bar is higher than the lower limit of another bar, that way you know they overlap
5. (Original post by Aimen.)
Hey, I know that's an awkward question but how do you delete a thread in here?
not a clue my dear, I'm just here to answer science questions :P
6. what GCSE grades did you get and any tips for people doing them now?
7. (Original post by issathemuslim1)
what GCSE grades did you get and any tips for people doing them now?
8 A*s 1 A, although that was only because I really pulled myself together in year 11. I was a slacker before year 11, did very little work and got "awful" year 10 module results (B's and C's), but about half way through year 11, I decided that I wanted to do something good with my life, so I got my **** together and did a few resits and revised hard and came out with some solid results. So my first bit of advice would be to revise :P and don't do what I did in year 10. Erm, as for other advice, I don't really know actually, I wasn't very good at studying for GCSEs, those grades were kind of flukes if anything, I mean, I had no idea what I was doing in most of my exams unlike at A levels where I actually had some clue as to how to study. GCSE was just kind of throwing everything at the wall and hoping something stuck and it paid off. So yh, I don't really have any proper tips, because my GCSE revision wasn't pretty organised. But I recommend making good notes, I did that for geog and history and got 99% and 97% in them respectively, and practise questions, that works best for maths, history and english.

Sorry that wasn't much help, I can offer some better A level revision advice for when you get to them :P
8. (Original post by AortaStudyMore)
Hey everyone, I am a medical student who doesn't really have time to do any proper, paid tutoring, however I am interested in teaching and helping people in general. I have tutored before, so if anyone is stuck on any GCSE/AS/A2 biology (or chemistry too for that matter) then feel free to ask and I'll help. Also if anyone has any questions about applying to medical school then I can help there too as I was in that position only last year, so it's fresh in my mind. I got 4 A's at AS and 3 A*s at A2 (bio, chem, maths, all above 95%)
9. (Original post by Wallflower73)
Thanks, sadly it comes at the cost of being absolutely awful with women :P But atleast I can label the components of a vertebra and describe how the greater and lesser omenta are formed! ..

But yh, work hard and you'll get good grades and no girls haha
10. ahahaha good point. who needs women when you've got bio!
i'm actually a girl.. lol and despite never having been in a relationship my grades are average I would say lol. ABB in AS (after resitting btw)

(Original post by AortaStudyMore)
Thanks, sadly it comes at the cost of being absolutely awful with women :P But atleast I can label the components of a vertebra and describe how the greater and lesser omenta are formed! ..

But yh, work hard and you'll get good grades and no girls haha
11. (Original post by Wallflower73)
ahahaha good point. who needs women when you've got bio!
i'm actually a girl.. lol and despite never having been in a relationship my grades are average I would say lol. ABB in AS (after resitting btw)
Hmm, I cannot agree with you on that "who needs women when you've got bio" comment aha, biology gets very boring very quickly! And they're good! Just don't do what I did, which was study too much, because it's not attractive it seems haha. I've had a fair few women like me, but they were all put off because I always had my nose in a textbook, and it's pretty depressing :P
12. It was actually a joke. It something I tell myself when I feel like a loner lol.
You still have time though. You can let loose for a while and throw that book away.
For me, it's not even about over reading. It's because I don't think i'm very interesting, that's why I'd rather sleep in my room haha
(Original post by AortaStudyMore)
Hmm, I cannot agree with you on that "who needs women when you've got bio" comment aha, biology gets very boring very quickly! And they're good! Just don't do what I did, which was study too much, because it's not attractive it seems haha. I've had a fair few women like me, but they were all put off because I always had my nose in a textbook, and it's pretty depressing :P
13. (Original post by Wallflower73)
It was actually a joke. It something I tell myself when I feel like a loner lol.
You still have time though. You can let loose for a while and throw that book away.
For me, it's not even about over reading. It's because I don't think i'm very interesting, that's why I'd rather sleep in my room haha
haha I'm glad, and nah, I'm sure you're not uninteresting, but anyway, I better get back to revising, so much anatomy to learn
14. oh good luck with your studying!
and don't forget to let loose okay
(Original post by AortaStudyMore)
haha I'm glad, and nah, I'm sure you're not uninteresting, but anyway, I better get back to revising, so much anatomy to learn
15. Hi, I was just wondering whether you could help me with restriction mapping/DNA sequences ^.^

How exactly can you work out the sequence of DNA by using restriction mapping (of long DNA fragments)? Im sure you'd use restriction endonucleases to cut up the DNA and then use DNA sequencing and Gel electrophoresis to work out the actual DNA sequence of each smaller fragment, but how would you then know the full sequence, because your original DNA is now cut up into smaller fragments so how would you know where to place the DNA fragments into their respective places?

Thank you! :-)

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16. (Original post by randoms132)
Hi, I was just wondering whether you could help me with restriction mapping/DNA sequences ^.^

How exactly can you work out the sequence of DNA by using restriction mapping (of long DNA fragments)? Im sure you'd use restriction endonucleases to cut up the DNA and then use DNA sequencing and Gel electrophoresis to work out the actual DNA sequence of each smaller fragment, but how would you then know the full sequence, because your original DNA is now cut up into smaller fragments so how would you know where to place the DNA fragments into their respective places?

Thank you! :-)

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Yh this is tricky, so the point of restriction mapping is to sequence DNA fragments rather than a whole length of DNA, because it's easier to sequence shorter pieces of DNA. As you've correctly pointed out, how do you know the order in which the sequence is? Well restriction mapping involves digesting DNA with individual restriction endonucleases, and then combinations of restriction endonucleases to allow you to piece together the DNA kind of like a jigsaw. I'll try my best to illustrate it with an example:

So let's say you have a 10kb (kilobase) length of DNA and you digest it with EcoRI and BamHI, and you end up with a 2kb, 3kb and 5kb fragment. What you obviously want to know is whether the order is 2, 3, 5 or 2, 5, 3 or 3, 5, 2 or 5, 3, 2 (the reverse orders do matter because 5, 3, 2 will not just be the reverse of 2, 3, 5). So this is where restriction mapping comes into it, if you digest with just EcoRI, let's say you get two 5kb fragments and if you digest with just BamHI, you get a 3kb fragment and a 7kb fragment. If you separate these out onto a gel electrophoresis, you'll see that EcoRI cuts the DNA straight down the middle, and then BamHI cuts on of the 5kb fragments into a 2kb and 3 kb fragment. So the sequence has to be either 2, 3, 5 or 5, 3, 2. The trick is to work out which way around it goes, well what happens is you radioactively label the first bit of your original DNA sequence, in this case let's assume that it's the 2kb fragment, this 2kb fragment will be the only radioactive one on the gel electrophoresis, and therefore it will be the first fragment, so the fragment order is 2, 3, 5.

Now, if you're like me, and you're questioning why 5, 3, 2 isn't just the reverse of 2, 3, 5, then let me just show you why:

Imagine these are the fragments

5'-AT-3'
3'-TA-5'

5'-GCA-3'
3'-CGT-5'

5'-ACTGA-3'
3'-TGACT-5'

2, 3, 5 will be:
5'-ATGCAACTGA-3'
3'-TACGTTGACT-5'

and 5, 3, 2 will be:
5'-ACTGAGCAAT-3'
3'-TGACTCGTTA-5'

clearly different.

^ You literally can't go wrong with that information, restriction mapping didn't come up in my exam, and as far as I know, it rarely does, but if you get your head around what I just said, then you should be able to do any restriction mapping question, I hope
17. (Original post by randoms132)
Hi, I was just wondering whether you could help me with restriction mapping/DNA sequences ^.^

How exactly can you work out the sequence of DNA by using restriction mapping (of long DNA fragments)? Im sure you'd use restriction endonucleases to cut up the DNA and then use DNA sequencing and Gel electrophoresis to work out the actual DNA sequence of each smaller fragment, but how would you then know the full sequence, because your original DNA is now cut up into smaller fragments so how would you know where to place the DNA fragments into their respective places?

Thank you! :-)

Posted from TSR Mobile
Obviously this isn't used these days, as we have full genome sequences now, as wiki puts it:
"Before sequencing was automated, it would have been prohibitively expensive to sequence an entire DNA strand. To find the relative positions of restriction sites on a plasmid, a technique involving single and double restriction digests is used. Based on the sizes of the resultant DNA fragments the positions of the sites can be inferred. Restriction mapping is a very useful technique when used for determining the orientation of an insert in a cloning vector, by mapping the position of an off-center restriction site in the insert (Dale, Von Schantz, 2003)."
18. (Original post by AortaStudyMore)
Yh this is tricky, so the point of restriction mapping is to sequence DNA fragments rather than a whole length of DNA, because it's easier to sequence shorter pieces of DNA. As you've correctly pointed out, how do you know the order in which the sequence is? Well restriction mapping involves digesting DNA with individual restriction endonucleases, and then combinations of restriction endonucleases to allow you to piece together the DNA kind of like a jigsaw. I'll try my best to illustrate it with an example:

So let's say you have a 10kb (kilobase) length of DNA and you digest it with EcoRI and BamHI, and you end up with a 2kb, 3kb and 5kb fragment. What you obviously want to know is whether the order is 2, 3, 5 or 2, 5, 3 or 3, 5, 2 or 5, 3, 2 (the reverse orders do matter because 5, 3, 2 will not just be the reverse of 2, 3, 5). So this is where restriction mapping comes into it, if you digest with just EcoRI, let's say you get two 5kb fragments and if you digest with just BamHI, you get a 3kb fragment and a 7kb fragment. If you separate these out onto a gel electrophoresis, you'll see that EcoRI cuts the DNA straight down the middle, and then BamHI cuts on of the 5kb fragments into a 2kb and 3 kb fragment. So the sequence has to be either 2, 3, 5 or 5, 3, 2. The trick is to work out which way around it goes, well what happens is you radioactively label the first bit of your original DNA sequence, in this case let's assume that it's the 2kb fragment, this 2kb fragment will be the only radioactive one on the gel electrophoresis, and therefore it will be the first fragment, so the fragment order is 2, 3, 5.

Now, if you're like me, and you're questioning why 5, 3, 2 isn't just the reverse of 2, 3, 5, then let me just show you why:

Imagine these are the fragments

5'-AT-3'
3'-TA-5'

5'-GCA-3'
3'-CGT-5'

5'-ACTGA-3'
3'-TGACT-5'

2, 3, 5 will be:
5'-ATGCAACTGA-3'
3'-TACGTTGACT-5'

and 5, 3, 2 will be:
5'-ACTGAGCAAT-3'
3'-TGACTCGTTA-5'

clearly different.

^ You literally can't go wrong with that information, restriction mapping didn't come up in my exam, and as far as I know, it rarely does, but if you get your head around what I just said, then you should be able to do any restriction mapping question, I hope
Oh woow - I understand. Yeah...those DNA fragments are so different

Thank you so much! You made it so much easier ^.^

Its so much clearer now ahahh, woop woop - thanks again!!

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19. Any general tips for edexcel igcse biology exam on Tuesday?
20. key words for beer production?

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