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A2 Biology OCR June 2015 Revision Thread

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Reply 900
Could anyone please tell me the different types of vegetative propagation?
So you have tissue culture/micro propagation and reproductive cloning. Are there any more?
Original post by a123a
Could anyone please tell me the different types of vegetative propagation?
So you have tissue culture/micro propagation and reproductive cloning. Are there any more?


veg prop is the growth of new structures on original ones (normally in plants etc)...they normally use the example of elms tree . I think the ones you mentioned are about artificial and natural cloning rather than vegetative prop
Reply 902
Original post by games211
veg prop is the growth of new structures on original ones (normally in plants etc)...they normally use the example of elms tree . I think the ones you mentioned are about artificial and natural cloning rather than vegetative prop


Oh ok that makes sense. Thank you!
Original post by cheeky 12
Oh no wait I I think DNA helicase basically just unwinds the two polynucleotide stands and then the RNA polymerase break the hydrogen bonds between the nucleotide bases


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I thought RNA polymerase associates free RNA nucleotides to the exposed DNA nucleotide bases during transcription to create mRNA?
how long does it take to learn off by heart all the basic information of F214, I'm doing 10 hours a day
Original post by ChoccyPhilly
I thought RNA polymerase associates free RNA nucleotides to the exposed DNA nucleotide bases during transcription to create mRNA?


I don't know! My book says RNA polymerase breaks hydrogen bonds
Original post by maisie__x
I don't know! My book says RNA polymerase breaks hydrogen bonds


No that's incorrect, RNA polymerase simply catalyses the binding of nucleotides to their complementary bases. DNA helicase is involved in unwinding the double stranded DNA and breaking the hydrogen bonds.
Original post by bbadonde2
No that's incorrect, RNA polymerase simply catalyses the binding of nucleotides to their complementary bases. DNA helicase is involved in unwinding the double stranded DNA and breaking the hydrogen bonds.


Right, thank you. :smile:
Original post by mybutton jammed
how long does it take to learn off by heart all the basic information of F214, I'm doing 10 hours a day

10 hours a day of purely biology f214?

It didn't take me long at all, and I wasn't doing nearly that many hours a day of f214...

F214 content is pretty simply, a lot of it is diagram based and processes. Make sure you know all of those, and you'll have the majority of marks under your belt :smile:
Original post by Cara_rose
10 hours a day of purely biology f214?

It didn't take me long at all, and I wasn't doing nearly that many hours a day of f214...

F214 content is pretty simply, a lot of it is diagram based and processes. Make sure you know all of those, and you'll have the majority of marks under your belt :smile:


yeh, revised last night from 9pm till 5am and pretty much covered about half of unit 4 will finish it off by today I think :biggrin:
The 'wolf' volcano has erupted in the Galapagos Islands today, what's the bets that OCR are gonna make next year's F215 paper pretty much based off this news and 75% of the paper will be based off that double paged spread in the textbook lol
Reply 911
Hey guys, I made a chatzy for biology so if you have any questions and stuff you can ask them there. :smile:

http://us20.chatzy.com/13203795560052
Can someone explain complementary epistasis please :smile: I understand recessive and dominant, but can't get my head around this one


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Original post by AsianBeauty
Can someone explain complementary epistasis please :smile: I understand recessive and dominant, but can't get my head around this one


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You basically need to dominant alleles for any characteristic to be displayed. So say you have two genes A/a and B/b, that code for flower colour:

Colourless compound --- A/a ---> Colourless Precursor --- B/b ---> Blue pigment

You need both a dominant A allele and a dominant B allele to get the blue pigment. So Aabb would give you colourless but AaBb would give you blue. It's a lot like recessive epistasis but with recessive epistasis as long as you have a dominant allele for the first gene you get a colour.
What are all the products of light independent stage of photosynthesis?
Thank you
Is there a whatsapp group for bio

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Original post by bbadonde2
You basically need to dominant alleles for any characteristic to be displayed. So say you have two genes A/a and B/b, that code for flower colour:

Colourless compound --- A/a ---> Colourless Precursor --- B/b ---> Blue pigment

You need both a dominant A allele and a dominant B allele to get the blue pigment. So Aabb would give you colourless but AaBb would give you blue. It's a lot like recessive epistasis but with recessive epistasis as long as you have a dominant allele for the first gene you get a colour.


Thank you so much. Makes sense now :smile:)


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Original post by bbadonde2
You basically need to dominant alleles for any characteristic to be displayed. So say you have two genes A/a and B/b, that code for flower colour:

Colourless compound --- A/a ---> Colourless Precursor --- B/b ---> Blue pigment

You need both a dominant A allele and a dominant B allele to get the blue pigment. So Aabb would give you colourless but AaBb would give you blue. It's a lot like recessive epistasis but with recessive epistasis as long as you have a dominant allele for the first gene you get a colour.


Can you explain recessive and dominant epistasis please ?
Original post by TheLegalDealer
Can you explain recessive and dominant epistasis please ?


Recessive epistasis is when you need a dominant allele of the epistatic first gene for the second hypostatic gene to be expressed. For example. Coat colour is controlled by the genes Z/z and G/g. For G/g gene to be expressed there must be a dominant allele for the Z/z gene.

Colourless compound --- Z/z ---> Grey ---G/g ---> Yellow.
If there is no dominant Z then G/g cannot be expressed. ZzGg will produce yellow. zzGG will be colourless. ZZgg will be grey, 9:3:4 ratio

Dominant epistasis is essentially the opposite. You need a recessive allele is the first epistatic gene for the second hypostatic gene to be expressed. Against Z/z and G/g for coat colour.

Colourless compound --- Z/z ---> Grey ---G/g ---> Yellow.
There needs to be a zz combination for the second gene to be expressed. zzGG will lead to yellow, zzgg will lead to Grey, ZzGG wil lead to colourless, ZZGG will be colourless. You need recessive homozygous in the first gene. 12:3:1 or 13:3 ratio
(edited 8 years ago)
So helpful ! Thank you so much ! Btw do we have to learn the raitos or is it better ti work it out ??

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