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    Does anyone have descriptions of escape reflexes ,kinesis and taxis? and an example of each?
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    (Original post by loperdoper)
    In the couple of times I've seen it, it's typically come up as describing what offspring look like, or it shows a metabolic pathway involving alleles and you can see that they're talking about dominant/recessive alleles. For instance, one year it had coat colours and it was saying that if it was ff, the colour would be x, but if it was FF/Ff, it would go to activate a compound which was controlled by another gene, and so on. It was pretty clear to see that it was discussing recessive epistasis.
    Could you explain what each type of epistasis is please
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    (Original post by ChoccyPhilly)
    Used in DNA replication, PCR

    Lines up free DNA nucleotides against exposed bases of a DNA strand

    That's it really.
    Also, it is described as thermophilic because it isn't denatured by extreme temperature. It is extracted from the species Thermus aquaticus
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    (Original post by Beni24)
    Does anyone have descriptions of escape reflexes ,kinesis and taxis? and an example of each?
    There we're quite a few answers on this some pages back, try 170 maybe
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    (Original post by sunshinebeem)
    What are the hardest F215 papers, I haven't got time to go through them all. Thanks


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    January 2011, grade boundary for an A was 60/100!
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    (Original post by cr7alwayz)
    Could you explain what each type of epistasis is please
    There are two main types (to the best of my recollection): dominant and recessive

    Epistasis revolves around the idea that one gene blocks the expression of another, so the types simply refer to what the alleles have to be for the blocking to take place.

    So, if it's recessive:
    You have Gene A and Gene B. Gene A has alleles A and a, Gene B has alleles B and b.
    If Gene B is recessive, it shows a blue colour. If dominant, a red colour.
    However, if Gene A is recessive, Gene B is blocked and it shows a green colour.

    Therefore, if two parents of AaBb genotypes are bred (both with have a red colour), they will have a 9:3:4 pattern. The 9 will refer to red offspring - Gene B has a dominant allele, and Gene A has a dominant allele. The 3 refers to blue offspring - Gene B is bb, but Gene A is still dominant. The 4 is for green offspring - Gene A is aa, which means Gene B could have any combination as it has been blocked by aa.

    If it's dominant, it's more or less the other way around.
    Using Gene C and Gene D. Gene C has alleles C and c, Gene D has D and d.
    If Gene D is recessive, it shows a purple colour. If it is dominant, it shows a pink colour.
    However, if Gene C has a dominant allele, the plant shows a yellow colour.

    Therefore, if two parents of CcDd geneotypes are bred, you have a ratio of 12:3:1. The 12 is for yellow offspring - Gene C has a dominant allele, making Gene D's alleles irrelevant. The 3 is for pink offspring when Gene C is cc, but Gene D has a dominant allele. The 1 is for purple offspring when Gene C is cc, and Gene D is dd.

    Dominant epistasis can also take on a 13:3 ratio.
    Gene E and Gene F.
    If Gene F is dominant, there is a violet colour. If Gene F is recessive (ff), no colour is produced and there is a white offspring.
    If Gene E is dominant, no colour is produced and there is a white offspring.

    Therefore, two parents with EeFf geneotypes have offspring of a 13:3 ratio. The 13 includes all dominant combinations of Gene E (EE/Ee/eE), as well as when Gene F is recessive (so, unlike 12:3:1, eeff is included in this). The final 3 is for when Gene E is recessive, but Gene F is dominant (eeFF, eeFf, eefF)
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    (Original post by Lizzieee4)
    Thank you so much. Do you use restriction endonuclease enzymes in PCR?
    I've got so many text books and they all contradict themselves this other one says there's different methods in sequencing it... So I'm guessing maybe my notes are one of the methods? Might just learn the text book one incase OCR don't like the method in my notes.... Thank you for your help
    Nope, the only enzyme in PCR (that I know of? Someone correct me if I'm wrong) is DNA polymerase You wouldn't need restriction endonuclease in PCR I don't think as you're not cutting up bits of DNA, you're only separating the DNA strands with heating/cooling and then sequencing strands using free DNA nucleotides, primers and DNA polymerase. Well, that's my take on it anyway :P It so annoying when textbooks contradict each other!
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    (Original post by Diamond Crafter)
    Thank you so much! And yes! The long awaited moment can't come any sooner! How about you?
    Yeah same. I would prefer if the biology exam would be on Friday or next week but yet again I can't wait for exams to be finally over! I am so looking forward to Wednesday after the exams!


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    What's the difference between homo/heterogametic and homo/heterozygous?
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    (Original post by Beni24)
    Does anyone have descriptions of escape reflexes ,kinesis and taxis? and an example of each?
    Seeing as all three of these are examples of innate behaviour, they're all automatic.

    Escape reflex: rapid response, organisms moving away from potential danger.
    e.g. ever notice you can't kill a cockroach 'cause they move so damn fast before you can squish 'em?

    Taxes: hey, sounds like "taxi", which is handy, because taxis move towards and away from a stimulus (i.e. the building they'll drop you off at/ pick you up from). In taxes, organisms do this, but they move towards/away from a DIRECTIONAL stimulus. e.g. a plant growing towards a light source that is placed in a particular place (I guess this is more positive phototropism though, thoughts anyone?)

    Kineses: doesn't the "Kine-" prefix mean something to do with movement in Latin or something? Anyway, remember this because it's an organism's movement response to a NON-DIRECTIONAL stimulus. e.g. woodlice move more slowly when it's damp/dark, and move fast in bright conditions to avoid predation. Stuff like intensity/humidity is non-directional.

    Hope that helped
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    (Original post by loperdoper)
    There are two main types (to the best of my recollection): dominant and recessive

    Epistasis revolves around the idea that one gene blocks the expression of another, so the types simply refer to what the alleles have to be for the blocking to take place.

    So, if it's recessive:
    You have Gene A and Gene B. Gene A has alleles A and a, Gene B has alleles B and b.
    If Gene B is recessive, it shows a blue colour. If dominant, a red colour.
    However, if Gene A is recessive, Gene B is blocked and it shows a green colour.

    Therefore, if two parents of AaBb genotypes are bred (both with have a red colour), they will have a 9:3:4 pattern. The 9 will refer to red offspring - Gene B has a dominant allele, and Gene A has a dominant allele. The 3 refers to blue offspring - Gene B is bb, but Gene A is still dominant. The 4 is for green offspring - Gene A is aa, which means Gene B could have any combination as it has been blocked by aa.

    If it's dominant, it's more or less the other way around.
    Using Gene C and Gene D. Gene C has alleles C and c, Gene D has D and d.
    If Gene D is recessive, it shows a purple colour. If it is dominant, it shows a pink colour.
    However, if Gene C has a dominant allele, the plant shows a yellow colour.

    Therefore, if two parents of CcDd geneotypes are bred, you have a ratio of 12:3:1. The 12 is for yellow offspring - Gene C has a dominant allele, making Gene D's alleles irrelevant. The 3 is for pink offspring when Gene C is cc, but Gene D has a dominant allele. The 1 is for purple offspring when Gene C is cc, and Gene D is dd.

    Dominant epistasis can also take on a 13:3 ratio.
    Gene E and Gene F.
    If Gene F is dominant, there is a violet colour. If Gene F is recessive (ff), no colour is produced and there is a white offspring.
    If Gene E is dominant, no colour is produced and there is a white offspring.

    Therefore, two parents with EeFf geneotypes have offspring of a 13:3 ratio. The 13 includes all dominant combinations of Gene E (EE/Ee/eE), as well as when Gene F is recessive (so, unlike 12:3:1, eeff is included in this). The final 3 is for when Gene E is recessive, but Gene F is dominant (eeFF, eeFf, eefF)
    The third type of epistasis is called complementary fashion, its in the OCR textbook page 129 but I don't understand that as well.
    Can anyone explain it?
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    (Original post by thequackingduck)
    What's the difference between homo/heterogametic and homo/heterozygous?
    pg 122 explains homo/heterozygous and pg 123 explains homo/heterogametic.
    I would explain but im behind on revision!
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    (Original post by cr7alwayz)
    The third type of epistasis is called complementary fashion, its in the OCR textbook page 129 but I don't understand that as well.
    Can anyone explain it?
    Oh, I forgot about that one (oops).

    For this one, genes need to work together in order to create a substance - the most likely explanantion is that one is an enzyme for another.
    Using Gene H and Gene I (G/g and I/i).
    If Gene H is recessive and/or Gene I is recessive, no colour will be produced, and it will appear white. Only if both Gene H and Gene I have a dominant allele will the offspring show colour.

    This provides a ratio of 9:7.
    The 9 is where a dominant allele is present in both genes - so this is HHII/HHIi/HHiI, HhII/HhIi/HhiI, hHII/hHIi/hHiI
    The 7 is where either gene has a recessive combination - so this is hhii, hhII/hhIi/hhiI, HHii/Hhii/hHii
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    Can someone very briefly explain how alleles spread throughout a population?
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    (Original post by Student23478)
    Can any 1 help me out for the june 2014 hardy Weinberg Eq it says dominant has brown colour and 45/60 in population are brown and says work out dominant frequency allele so why do you do 15/60 instead of 45/60???
    It gives you the genetype for the recessive not the dominant 45/60 is dominant 60-45=15 so 15/60 is q^2 (basically the dominant could be homozygous or heterozygous so u wouldn't know whether to use q^2 or 2pq so it makes sense doing q^2 which is deffo homozygous recessive)

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    predictions?
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    (Original post by thequackingduck)
    What's the difference between homo/heterogametic and homo/heterozygous?
    homogametic is XX or YY whereas heterogametic has one X and one Y

    heterozygous means two different alleles and homozygous is two of the same alleles
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    (Original post by baymax96)
    homogametic is XX or YY whereas heterogametic has one X and one Y

    heterozygous means two different alleles and homozygous is two of the same alleles
    Thank you!!
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    (Original post by coolerthanbeans)
    Nope, the only enzyme in PCR (that I know of? Someone correct me if I'm wrong) is DNA polymerase You wouldn't need restriction endonuclease in PCR I don't think as you're not cutting up bits of DNA, you're only separating the DNA strands with heating/cooling and then sequencing strands using free DNA nucleotides, primers and DNA polymerase. Well, that's my take on it anyway :P It so annoying when textbooks contradict each other!

    Makes sense. Thank you very much
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    (Original post by Klesia)
    HOW ARE WE MEANT TO GET THE WHOLE OF F215 IN OUR HEADS?

    feel like my brain is going to explode!
    I feel you!!!!!!😭😭😭


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