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A2 Biology OCR June 2015 Revision Thread

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Reply 3640

em_mahoney

Epistasis makes me want to cry and stab myself repeatedly with a fork why does it exist

Reply 3641

tewas

does anyone have a summary of grade boundaries?

Reply 3642

bakedbeans247

Original post by purplecloud

the jan 2012 paper was so hard and its 68 for an A like wtf

Whaat? I was thinking the opposite, that's one of the only papers i can actually do decent...There were like 3 big questions with fill in the gaps lol

Reply 3643

mushyD

Original post by corey7695

you don't know anything at all?

I could probably get 20/100 with my current knowledge

Reply 3644

plumpOlhenry

Original post by em_mahoney

Epistasis makes me want to cry and stab myself repeatedly with a fork why does it exist

To mask that behaviour LOL

2 hour exam woooo

Original post by cinderella25

i can get all the other questions right but i can never get this right, i cant see where i am going wrong. can someone explain this to me?

Two pure breeding strains of snapdragon, a garden plant, were obtained. Onestrain had red flowers and the other had white flowers. The two strains werecrossed yielding F1 plants all with pink flowers. The F1 were then interbred toproduce F2 plants with the following colours:

red 62
pink 131
white 67

The following hypothesis was proposed:Flower colour is controlled by a single gene with two codominant alleles.
(b) Complete the genetic diagram to explain this cross.

Use the following symbols to represent the alleles:Cr= red, Cw= white

Parental phenotypes: red flowers x white flowers

Parental genotypes: .................................... ........................................ Red: CrCr White: CwCw

Gametes: .................................... ........................................ Red: Cr White: Cw

F1 genotypes: .................................................................................................All CrCw

.F1 phenotypes: ................................................................................................
All are pink
Gametes: ........................................................................................................ Cr or Cw

F2 genotypes: .................................................................................................. CrCr, 2x CrCw or CwCw

F2 phenotypes: ................................................................................................
Red: Pink : White
Expected F2 phenotypic ratio:......1:2:1...................................................................

Tried to answer this the best I could, hope this helps!

Reply 3647

purplecloud

how do you work out 1cii on the june 2012 paper?

Reply 3648

THEMathlete

Learning the steps of sequencing a genome... So so screwwwed

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Reply 3649

jessicadanby1996

As last years paper had a bit about cloning frogs, is it unlikely that animal cloning will come up?

Reply 3650

Lychees

with sequencing the genome in the ocr book there seems to be 2 ways to do it. one using BACS and the other using labelled nucleotides etc a couple of pages ahead. if a question were to come up about sequencing the genome which one would i use