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F215 - Revision thread 13th June 2011

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In the ocr heinemann book on 2.2 spread 4, do we need to know all the examples listed in the table or is it just the paragraph below the table we need to know?
Thanks

Reply 1601

mazam

They're called terminator bases. Theyre thrown off the fluorescent markers.

Reply 1602

greenford

for people stressing about genome sequencing

my teachers said that its highly unlikely that there will be a long question on genome sequencing... the kind of question they could ask are:
Describe PCR
Explain chain terminating method
Explain electrophoresis
or describe BAC

Reply 1603

science rules! :)

Original post by rebeccalouise_92

can anyone tell me, you know in interrupted PCR... what is it exactly that means the dna polymerase is thrown off when it comes to a died base? something is missing that isn't complementary i think :s ....

Intrrupted PCR has many similarities to normal PCR (and also DNA replication). The sequencing mixture consists of primers, DNA polymerase, single stranded template DNA fragment, free DNA nucleotides. However in interrupted PCR teh sequencing mixture also contains modificed nucleotides (which carry a fluorescent marker).

Modified nucleotides (with a fluorescent marker) cause chain termination. When added, this throws DNA polymerase off and prevents any further free nucleotdies being added to the chain. So, in interrupted PCR teh end of the strand is always a modified nucleotide carrying a fluorescent marker.

Other similarities of PCR and interrupted PCR are that they both allow extention of the double stranded DNA molecule by the addition of the enzyme DNA polymerase.

DNA nucleotides bind by complementary base pairing (using hydrogen bonds) in both.

Reply 1604

R.Fanatic

Original post by Kidms001

I took both too :yep:

.. I feel that Physics is slightly easier, but Biology is far more interesting content wise :holmes:

:O I took both too.. Physics is more interesting for me....Biology sorta gets on my neurones :erm:

(pun intended :tongue:

)

Reply 1605

science rules! :)

Original post by greenford

Oh, we like a bit of describe PCR!

The DNA sample is mixed with DNA nucleotides and the enzyme DNA polymerase.
The mixture is heated to 95 degrees and the hydrogen bonds between complementary base pairs break. A single stranded piece of DNA is formed.

Primers are added (short single stranded pieces of DNA 10-20 nucleotide bases long)

The temperature is reduced to 55 degrees and the primers anneal onto the single stranded piece of DNA by complementray base pairing (using hydrogen bonds).
Small sections of double stranded DNA are at either end of the sample.

The temperature is raised to 72 degrees and the enzyme DNA polmerase is added. thi is the optimal temperature for this enzyme.

The enzyme extends the double stranded DNA by adding free nucleotides. A double stranded DNA molecule is formed.

It is a cyclic process, repeated many times. The amount of DNA increases exponentially (x2, x4, x8 etc)

Remember... PCR is can eb used to produce multiple copies of DNA fragments (amplifies small fragments of DNA)

Reply 1606

science rules! :)

Original post by science rules! :)

But.. How would we describe BAC?! :confused:

Reply 1607

mazam

Does anyone have the january 2011 paper and mark scheme ?

Reply 1608

heartskippedabeat

Original post by mazam

Does anyone have the january 2011 paper and mark scheme ?

Page 12 of this thread :smile:

Reply 1609

heartskippedabeat

Do people think it's better to stay up all night revising tonight or tomorrow night? I was thinking tonight so I get some sleep before the exam but I'm not sure :tongue:

It'll probably end up being both nights though haha

Reply 1610

mazam

Original post by heartskippedabeat

Page 12 of this thread :smile:

Thanks i found it

Reply 1611

Waqar Y

Original post by YuDunno

Wow.. thanks for that Waqar :smile:

remind me to pos rep you tomorrow!

- The Gibberellins promote seed germination
- I don't think we need to know how but just for the record.. you need malt to make beer.. when barley seeds germinate the aleurone layer of the seed produces AMYLASE enzymes to break down the stored STARCH in to MALTOSE, usually the genes for amylase production are switched on by naturally occuring gibberellins, if you add gibberellins urself, you can speed this process up :smile:

..dry and grind up seeds to make malt.

I have a feeling this could turn in to a lac operon-ish q..

anywaysss.....

Neuromuscular junction? synapse?

differences/similarities to neurotransmitter junctionn?

Neuromuscular junction - synapse between nuerone and muscle fibre

1) Action potential arriving causes depolarization of pre-synaptic membrane
2) Calcium ion channels open and calcium ions fuse with vesicles containing the nuerotransmiter acetylcholine
2) Released by exocytosis, diffuses across the synaptic cleft and binds to receptors on the sacrolemma
3) This causes depolarization, due to NA+ gates opening, depolarization wave causes depolarization of T-tubules which are inner folds of the sarcolemma. Helps conduct the depolarization wave.
4) Reaches the sarcoplasmic reticulum, calcium ions are released and bind to troponin, which changes the shape of tropomyosin, allowing for muscular contraction to occur.

Synapse - junction between two or more neurones

It's pretty much similar to what I said, except that it's the post-synaptic membrane and transmits a nervous impulse.

-------

Similarities - both use chemical synapses
- both have receptors on the post-synaptic membrane
- both cause some form of response
- both are broken down by enzymes, e.g aCHE breaks down aCH

Differences -NM junction always uses acetylcholine, other neurotransmitters are
dopamine, noradrenaline(only binds to adrenal medulla!)
-The postsynaptic membrane shape is different, normally it's jagged on
the sarcolemma
- Fewer receptors at synapses, because only a small amount is needed
to generate an action potential
- One is involved in muscular contraction, other is involved in
transmitting an action potential.

Anything else haha? this is all from memory, can't believe i store this much info :|

Reply 1612

ekta9

Someone explain apical dominance please.. as in the evaluating the evidence bit?! :biggrin:

Reply 1613

Waqar Y

Original post by heartskippedabeat

Do people think it's better to stay up all night revising tonight or tomorrow night? I was thinking tonight so I get some sleep before the exam but I'm not sure :tongue:

It'll probably end up being both nights though haha

i wouldn't recommend staying up tommorow night, you need to have some rest too :smile:

the exams in the afternoon so i'm sure you could get a few hours done then?

Reply 1614

Waqar Y

Original post by ekta9

Someone explain apical dominance please.. as in the evaluating the evidence bit?! :biggrin:

Allrighty, basically apical dominance is when the growing apical bud inhibits the growth of the lateral bud(side shoots)

There's experimental evidence for this because:

-If you remove the apical bud, side shoots grow and apical dominance doesn't occur
-If you apply synthethic auxin, but remove the apical bud, the side shoots won't grow

Reply 1615

786girl

*
Describe the role of the brain and nervous system in coordinated muscular movement...

??? how would you answer that

Reply 1616

sportycricketer

Original post by greenford

If thats the case, it shouldn't be too bad :biggrin:

Reply 1617

sportycricketer

Can someone please help me with Succession? I know it and understand it but I was wondering if someone had an "easier" and summed up version of it which I might be able to write about in an essay form in the exam? This is for sand dunes btw :smile:

Would be greatt!

Reply 1618

heartskippedabeat