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Hi, would someone be able to explain to me the point of electrophoresis? I don't understand why having the shards in order of length would be beneficial to finding out the sequence?
Original post by KieranMPK
Hi, would someone be able to explain to me the point of electrophoresis? I don't understand why having the shards in order of length would be beneficial to finding out the sequence?


The principle of electrophoresis is that amino acids are attracted by the electrodes based on their electronegativities. If I'm not mistaken, the amino acids with a high electronegativity are attracted by the minus pole, while amino acids with a low one are attracted by the plus pole. So it is possible to distinguish an amino acid from another one.
Original post by KieranMPK
Hi, would someone be able to explain to me the point of electrophoresis? I don't understand why having the shards in order of length would be beneficial to finding out the sequence?


As Kallisto mentioned, it can be used for separating amino acid fragments based on size or charge. It's mainly used to separate DNA fragments based on their size. The main idea being that you can identify the DNA fragment of interest, and you can then purify the product and sequence it. You generally don't use gel electrophoresis if you just want to find the sequence of the whole genome.

I suppose you could use electrophroesis as a control to work out whether or not your sample is contaminated, and screen for primer dimers, but that's more on the process of electrophoresis and you won't need to know about that for A-levels.
Original post by Kallisto
The principle of electrophoresis is that amino acids are attracted by the electrodes based on their electronegativities. If I'm not mistaken, the amino acids with a high electronegativity are attracted by the minus pole, while amino acids with a low one are attracted by the plus pole. So it is possible to distinguish an amino acid from another one.


Original post by Eloades11
As Kallisto mentioned, it can be used for separating amino acid fragments based on size or charge. It's mainly used to separate DNA fragments based on their size. The main idea being that you can identify the DNA fragment of interest, and you can then purify the product and sequence it. You generally don't use gel electrophoresis if you just want to find the sequence of the whole genome.

I suppose you could use electrophroesis as a control to work out whether or not your sample is contaminated, and screen for primer dimers, but that's more on the process of electrophoresis and you won't need to know about that for A-levels.


Thanks a lot, It's not very clear in the book!
Original post by KieranMPK
Thanks a lot, It's not very clear in the book!


You are welcome!

Original post by Eloades11
(...) The main idea being that you can identify the DNA fragment of interest, and you can then purify the product and sequence it. (..)


That sounds very interesting! but how to purify a DNA sequence? and why it is used?
Original post by Kallisto


That sounds very interesting! but how to purify a DNA sequence? and why it is used?


It's quite a clever process. The are many various applications for this technique, but I'll just give an example of one I've come across in one of my projects. What I was doing over a summer project was looking for single nucleotide polymorphisms (SNP) in late bolting lines in lettuce. Previous research had identified markers which we used to screen for the SNPs, identifying for where one parent had a guanine residue, the other had an adenine (basically just different nucleotides). We had to design primers and amplify DNA sequences surrounding these markers in late bolting lines, and we run these amplified products on gel electrophroresis to identify the expected fragment size estimated by the primer design.

We run these on gel, using a control which had water added instead of DNA to identify primer dimers. If we identified the expected fragment in the correct lane, there were 2 ways to isolate and purify the DNA. The purification process is just to basically clean the isolates before they are sent for sequencing. We can either take the PCR product directly and clean the sample, although you have to make sure there weren't any other DNA products on the gel electrophoresis, otherwise they will be sequenced and we don't want that. If there were other bands on the gel present, then we would have to run the whole PCR product on a larger gel, and then extract the DNA sample from the gel in the dark room using UV light. The process of both DNA purification methods is hyperlinked here using the Qiagen QIAquick PCR purification kit (which is quite an expensive kit!).

This is a research paper quite similar to what my project was on: http://link.springer.com/article/10.1186%2F1471-2229-9-135#page-1
Can someone explain sex linkage to me please?!
Reply 207
Original post by jenigma
Can someone explain sex linkage to me please?!


I think it's basically just when a gene is present on either the x or y (non autosomal) chromosomes and so the condition it caused will be 'sex linked'
Like if it's on the X chromosome, any male who has it, even if it's recessive will have the condition as they only have 1 x chromosome and 1 y, where as a female heterozygote would not have the condition.


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Can anyone tell me whether the part of the retina which is responsible for colour vision has lesser neuronal connectivities than the part of the retina which is responsible scotopic vision? Its about the human eye!
Reply 209
Can anyone explain what the roles of synapses are?
Reply 210
Original post by HarryMWilliams
It's a pretty big question. How would you go about answering it first of all?


could you please help me with the question asked above by me?
Original post by 333obi
Can anyone explain what the roles of synapses are?


Synapses allow the transmission of an electrical signal from one cell to another. This can be a purely electrical synapse where gap junctions between the two cells transmit the current or it can be a chemical synapse where a chemical neurotransmitter is involved.

Electrical synapses are good for rapid transmission between cells but there is a problem, which brings me on to another important role of a synapse. If you imagine a cell synapsing with another - the small axon attaches on to a larger cell body. Remember from physics that small wires have a large resistance and hence small current and large wires have a small resistance and large current. All this means that when a small axon synapses with a large cell body then it is unlikely that an action potential will be triggered without some means of amplification. Chemical neurotransmitters act to amplify the signal and rectify this problem.
Original post by Asklepios
x

Original post by 333obi
x


Beaten to it by an awesome TSR Study Helper! :biggrin:
Reply 213
Original post by Asklepios
Synapses allow the transmission of an electrical signal from one cell to another. This can be a purely electrical synapse where gap junctions between the two cells transmit the current or it can be a chemical synapse where a chemical neurotransmitter is involved.

Electrical synapses are good for rapid transmission between cells but there is a problem, which brings me on to another important role of a synapse. If you imagine a cell synapsing with another - the small axon attaches on to a larger cell body. Remember from physics that small wires have a large resistance and hence small current and large wires have a small resistance and large current. All this means that when a small axon synapses with a large cell body then it is unlikely that an action potential will be triggered without some means of amplification. Chemical neurotransmitters act to amplify the signal and rectify this problem.


Hiya, thanks for that. The ocr book has specific answers such as, converging of the signal, diverging of the signal, acclimatisation, summation and to ensure that the signal travels in one direction.

What do they mean by these terms? thank you
Reply 214
Original post by HarryMWilliams
Beaten to it by an awesome TSR Study Helper! :biggrin:


You can have a go at my additional question :colondollar:
Hello, I have a question regarding the Light-independent stage of photosynthesis.
During the formation of TP, what happens to the H+ ions that come from recycling reduced NADP to NADP and how does it help reduce GP to TP?
Sorry if it's a silly question, my textbook doesn't explain this and it's frustrating me.

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Original post by TheBlueBiro
Hello, I have a question regarding the Light-independent stage of photosynthesis.
During the formation of TP, what happens to the H+ ions that come from recycling reduced NADP to NADP and how does it help reduce GP to TP?
Sorry if it's a silly question, my textbook doesn't explain this and it's frustrating me.

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Reduction is gain of H, so H is lost from reduced NADP to form NADP and this H is transferred to GP. GP gains H so is reduced. :smile:

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Original post by Claree
Reduction is gain of H, so H is lost from reduced NADP to form NADP and this H is transferred to GP. GP gains H so is reduced. :smile:

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Thank you so much!! Haha, I knew it would be something simple, my mind was just so jumbled up I couldn't think of a reasonable answer! :biggrin:

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Can someone please help me? Any extra information explaining the answer would be great too! Thanks

During endocytosis, vesicles are formed from the plasma membrane and pass into the cytoplasm.
Any glycoprotein that enters the cell as part of the vehicle is broken down by enzymes in the lysosomes.
In an inherited disease called Hunter's syndrome, one of the enzymes needed to hydrolyse the polysaccharide chains is absent. Polysaccharide's remain in the lysosomes until the cell eventually dies.
a) Many body tissues are affected by Hunter's but the different tissues are not affected to the same extent. Suggest an explanation for this observation.
b) Cells from an individual with Hunter's syndrome appear different to normal cells when viewed with an electron microscope. Suggest one way in which they would appear different.

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Original post by 333obi
Hiya, thanks for that. The ocr book has specific answers such as, converging of the signal, diverging of the signal, acclimatisation, summation and to ensure that the signal travels in one direction.

What do they mean by these terms? thank you


Converging of the signal: multiple stimuli combine to cause on response
diverging... : one stimulus causes multiple responses
acclimatisation: all vesicles of neurotransmitter have been used, so no more action potentials can be produced-non harmful stimulus is ignored
summation: the process under which an action potential is produced in the post-synaptic neurone (either one stimulus repeatedly sending action potentials or multiple stimuli at once)

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