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Edexcel igcse biology may 2012 exam discussion

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Avatar for Siiba
Siiba
Original post by *Mariya*
does anyone have the markscheme for may 2005 paper 2h?


I don't think there is one of the Edexcel website for some reason, but there is a sample of someones paper that is on there. I think it's under Exmplar something..you could also look around Google and stuff...
would i get the marks if my example of biological control was spiders being the control and flies being the pest?
Why is poo yellow?


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Wait that isn't on the syllabus.

But can someone answer it?


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Original post by Umackjiggles
you use restriction endonucleases in order to isolate and extract the gene for resistance to cold temperatures(for example). You then use the same restriction endonucleases on the plasmid of the bacteria Agrobacterium. You then mix the two together and they stick together on account of their sticky-ends. You then add DNA Ligase in order to hold them permenantly together. You then add a solution contain the plasmid which acts as a vector and you pour it into a petri dish with leaves (explants) from the plant you want to modify. The explants should take up the plasmid thus creating a genetically modified plant with a resistance to cold temperatures thus increasing the expected yield of the crop.


Surely you need the solution to contain the whole bacteria (agrobacterium), not just the plasmid? If it was unnecessary for agrobacterium to infiltrate the plant cell and inject its plasmid in, you could just use any plasmid (you wouldn't necessarily need an agrobacterium plasmid). And then, the agrobacterium would be the vector, I think?
Original post by Tentinator
Wait that isn't on the syllabus.

But can someone answer it?


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Bump


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Original post by Big-Daddy
Surely you need the solution to contain the whole bacteria (agrobacterium), not just the plasmid? If it was unnecessary for agrobacterium to infiltrate the plant cell and inject its plasmid in, you could just use any plasmid (you wouldn't necessarily need an agrobacterium plasmid). And then, the agrobacterium would be the vector, I think?


That is correct, sorry I seem to have confused regular GM with Plant-specific GM which is a bit retarded on my part :smile: .
Original post by Umackjiggles
That is correct, sorry I seem to have confused regular GM with Plant-specific GM which is a bit retarded on my part :smile: .


Ah, I see, fair enough. :smile: But in regular GM, there's no need for agrobacterium - you can just transfer a gene from one plasmid to the other (assuming that both organisms have plasmids to start with). Also, would you use a solution containing agrobacterium with the explants, or just "apply" the agrobacterium to a fully grown plant cell? (I have no idea, I was wondering if you could clarify ... I've heard of these "tumours" or things like that in my Biology class, but I don't understand what the relevance of that is.)
Reply 548
Avatar for goxy
goxy
please could someone explain production of beer so that its understandable ?? :s-smilie:
Original post by Big-Daddy
Ah, I see, fair enough. :smile: But in regular GM, there's no need for agrobacterium - you can just transfer a gene from one plasmid to the other (assuming that both organisms have plasmids to start with). Also, would you use a solution containing agrobacterium with the explants, or just "apply" the agrobacterium to a fully grown plant cell? (I have no idea, I was wondering if you could clarify ... I've heard of these "tumours" or things like that in my Biology class, but I don't understand what the relevance of that is.)


you would use it on explants that take it up and then you would grow them in a culture medium as per micropropagation. Not sure what this tumour you mention is.
What is a zygote.


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What is a uterus


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How is sperm suited for its needs.

Like its swimming nature


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Reply 553
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goxy
zygote is seed in fruit two fused nucei of plant gametes
Original post by Tentinator
What is a zygote.


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A zygote is a diploid cell that is formed after the fusion of the nuclei of the male and female gametes in fertilisation.
Are the sex positions tested in this exam. Like 69


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Reply 556
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goxy
umackjiggles could u answer my question please?? :smile:
Original post by goxy
umackjiggles could u answer my question please?? :smile:


**** off


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Let him answer my questions first.


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I have a feeling there will be a comprehension on the heart.


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