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Ocr f215: 27/1/11

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Original post by mathsclown
Quick epistasis question can homozygous recessive ever mask the expression of a dominant homozygous or heterzygous at the 2nd locus?
Edit: Doesnt matter figued it out


What is the answer lol?
Original post by aimz08
Seriously struggling ahhhhhhh
Had a really bad chemistry paper this morning and now this :s-smilie:

Any tips...anything particular I should learn?


Make sure you can right the main things from scratch for big essay questions

ie succession, protein synthesis, lac operon, nitrogen cycle etc
Original post by aimz08
Seriously struggling ahhhhhhh
Had a really bad chemistry paper this morning and now this :s-smilie:

Any tips...anything particular I should learn?


Ehm not too sure really

definetly get the genetics bit, meiosis, natural and artifical selection, nitrogen cycle, animal responses and behaviour, genomes and gene therapy, genetic engineering
and succession

Not too sure what will come up, very random paper :/
Original post by SwordStream
What is the answer lol?


Its complementary epistasis, came up in June lol thats how I figured it out xD
basically the homozygous prescence of a recessive allele at either locus, prevents expression of genes on the other locus

arrgh feeling mixed about the exam :/ really hoping its a straightforward paper
Reply 184
Avatar for aimz08
aimz08
13
Original post by mathsclown
Ehm not too sure really

definetly get the genetics bit, meiosis, natural and artifical selection, nitrogen cycle, animal responses and behaviour, genomes and gene therapy, genetic engineering
and succession

Not too sure what will come up, very random paper :/


Natural and Artificial selection - breadwheat and the other thing can someone explain that?
Original post by mathsclown
Its complementary epistasis, came up in June lol thats how I figured it out xD
basically the homozygous prescence of a recessive allele at either locus, prevents expression of genes on the other locus

arrgh feeling mixed about the exam :/ really hoping its a straightforward paper


I hope it's more straight forward than that tomorrow.
Original post by aimz08
Natural and Artificial selection - breadwheat and the other thing can someone explain that?


Tristium aestivum bread wheat is a hybrid with 42 chromosomes with the genotype
A^uA^u (from wild wheat) BB(from T.turidum) and DD(from wild goat grass)

Ok, Start off with WILD EINKORN this has genotype AuAu and 14chrom; domestication and aritficcial selection has altered the phenotype but not the chromosome number.

Now, cross the Einkorn (14chrom) AuAu with Wild grass BB (14 chromosomes)
The result is a sterile hybrid P, with genotype AuB, a mutation doubles the chromosome number, this is polyploidy, and the result is EMMER wheat with 28chromosomes genotype AuAuBB

Now cross this EMMER WHEAT AuAuBB (28chrom) with wild goat grass DD (14chrom)

The result is a sterile hybrid, Q,AuBD, a mutation doubles the chromsome number (polyploidy) and we get modern bread wheat AuAuBBDD with 42 chromosomes

The characterisitics focused on are, straw stiffness, resistance to lodging and fungal infection and a high protein content
Original post by SwordStream
I hope it's more straight forward than that tomorrow.


Yup same, aiming for a high C or a B, then retake an AS unit in june to push my final grade up to a B, always hated biology, this is the first time ive done proper revision for a bio exam, but still this is the hardest unit i guess

Got an A in chemistry and a B in maths last summer, retook 2 maths units think ive pushed it up to an A now, bio got a C overal last summer and thast what is dragging me down
(edited 13 years ago)
Reply 188
Avatar for Olivia001
Olivia001
Nervousss!!!
I need a B overall. Planning to go study Biology at uni in sept lol.
Original post by SwordStream
I need a B overall. Planning to go study Biology at uni in sept lol.


June paper 59marks was a B, so I think if its of similar difficulty then all we have to do is get the essay questions right, use common sense on the annoying "suggest" questions and pray from there on out lol :biggrin:
Reply 191
Avatar for aimz08
aimz08
13
Original post by mathsclown
June paper 59marks was a B, so I think if its of similar difficulty then all we have to do is get the essay questions right, use common sense on the annoying "suggest" questions and pray from there on out lol :biggrin:


Feel like making a list for essay questions? :P
Original post by aimz08
Feel like making a list for essay questions? :P


Ill give it a go lol, taking a break from revision done module 1 and 2 starting number 3 in a mo

Hmmm essay questions im guessing will come from:
Protein synthesis (transcription and translation)
Lac Operon (remember the mechanism, and what each part of it does)
Apoptosis (sequence of events)
Meiosis (doubt there'll be an essay on the whole thing because that would be something like 20marks lol, but still learn each division stage and learn how meiosis and fertilisation leads to genetic variation because that is more likely to be the essay question)
Artificial selection how its lead to production of modern dairy cows and modern bread wheat

Cloning (natural and artificial propagation, animal cloning)
Genomes (how to sequence)
PCR
Electrophoresis
Genetic enginneering (insulin, golden rice and replica plating)
Gene Therapy (most likely to be either somatic vs germ line or the ethical issues)

Succession
Nitrogen Cycle
Sustainable management (coppicing, felling clearing etc)
Galapgos Islands (human activity: increase in population, hunting/fishing, introduction of indeginous species)

Roles of hormones in leaf loss in deciduous plants (cytokinins, abiscic acid and auxin and ethene)
Everything on muscles lol
Behaviour maybe in terms of compare each one
Has anyone got any good notes for the nitrogen cycle? :smile:
Original post by Casper266
Has anyone got any good notes for the nitrogen cycle? :smile:


courtesy of ibsaiyan :smile:

Nitrogen on its own is a very stable atom (covalent triplet bond) hence is unreactive and of no good to living organisms.It's converted into ammonium by nitorgen fixing bacteria called Rhizobium.These bacteria live in free soil and mutual relationship with leguminous plants.In free soil their conversion capacity is limited.They are found in the root nodules of the plant.
How do they get in there?
When these plants germinate,they release a protein called lectin which binds onto the cell wall of the bacteria.Bacteria are attracted to the root and in doing so they stimulate the plant to form lumps so that they colonize it.The enzyme produced by these bacteria is nitrogenase which catalyzes nitrogen to ammonium. (this is reduction)
To do this the bacteria requires:
1)Hydrogen ions- From reduced NADP
2)ATP-From sucrose made by the plant in photo.synthesis
3)Anaerobic condition

Plants make the use of ammonium to build proteins.Once organisms assimilate them they are reformed into proteins.Decomposing bacteria break down part of proteins into ammino acid for their use and rest into Ammonia.Ammonia gets quickly converted into Nitrite and then Nitrate by nitrifying bacteria called Nitrosomonas and Nitrocbacter.These gain energy by the conversion.They require aerobic condition.Denitrifying bacteria do opposite of nitrogen fixation they convert nitrates back into Nitrogen.
(edited 13 years ago)
Hey, I'm glad to see I'm not the only one retaking this :smile: I just scraped a B on this before, I need to improve by 11ums to get my Biology grade overall to an A. I'm not feeling as confident about this as the chemistry paper I did earlier! I'm really hoping that OCR don't throw one of their traditional random questions in.
Also does anyone know if we would be given the Hardy-Wienberg equations or if we have to learn them?
Original post by mathsclown
courtesy of ibsaiyan :smile:

Nitrogen on its own is a very stable atom (covalent triplet bond) hence is unreactive and of no good to living organisms.It's converted into ammonium by nitorgen fixing bacteria called Rhizobium.These bacteria live in free soil and mutual relationship with leguminous plants.In free soil their conversion capacity is limited.They are found in the root nodules of the plant.
How do they get in there?
When these plants germinate,they release a protein called lectin which binds onto the cell wall of the bacteria.Bacteria are attracted to the root and in doing so they stimulate the plant to form lumps so that they colonize it.The enzyme produced by these bacteria is nitrogenase which catalyzes nitrogen to ammonium. (this is reduction)
To do this the bacteria requires:
1)Hydrogen ions- From reduced NADP
2)ATP-From sucrose made by the plant in photo.synthesis
3)Anaerobic condition

Plants make the use of ammonium to build proteins.Once organisms assimilate them they are reformed into proteins.Decomposing bacteria break down part of proteins into ammino acid for their use and rest into Ammonia.Ammonia gets quickly converted into Nitrite and then Nitrate by nitrifying bacteria called Nitrosomonas and Nitrocbacter.These gain energy by the conversion.They require aerobic condition.Denitrifying bacteria do opposite of nitrogen fixation they convert nitrates back into Nitrogen.


Thank youu!!! I must of missed this! :smile: hope everyones prepared for tomorrow!
Original post by Adventure10
Also does anyone know if we would be given the Hardy-Wienberg equations or if we have to learn them?


Nice with the B, I would of been over the moon !
Ehm good question and seriously not sure so to be on safe side, we should learn them not to tough


p + q = 1
p^2 + 2pq + q^2 = 1
And the assumptions made when carrying it out are just: any mating is random, population is large, no genotype has a selective advantage and errr there is no mutation, migration or genetic drift
Have you guys attempted the specimen?

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