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    (Original post by Remarqable M)
    Someone please summarise for me Epistasis
    that damn chicken on page :banghead:
    From the top of my head: Epistasis is the process in which one gene is switched off/on by another gene or a gene which controls appearance of another gene err... just like the black coat of mice. Correct me if i am wrong.
    Add to that: White being recessive but strangely one would think Black being the dominant which it isn't instead agouti is.
    More Answers will be posted later on by me .
    Here is my easter plan:
    3 Hrs x Physics
    3 Hrs x Maths
    2 Hrs x Biology resitting f212,214 too
    EDIT: Chicken,lol which book is that ?Mary Jones.
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    (Original post by I Have No Imagination)
    Hey guys, I just discovered this guy, he's pretty amazing.

    http://www.mefeedia.com/feeds/92219/...-videos/oldest
    Great presentation.Thanks
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    (Original post by ibysaiyan)
    From the top of my head: Epistasis is the process in which one gene is switched off/on by another gene or a gene which controls appearance of another gene err... just like the black coat of mice. Correct me if i am wrong.
    Add to that: White being recessive but strangely one would think Black being the dominant which it isn't instead agouti is.
    More Answers will be posted later on by me .
    Here is my easter plan:
    3 Hrs x Physics
    3 Hrs x Maths
    2 Hrs x Biology resitting f212,214 too
    EDIT: Chicken,lol which book is that ?Mary Jones.
    I'd avoid talking about mice coat colour, as that's co-dominant, which confuses the subject a bit more.

    Epistasis is the interaction between two unlinked (not on the same chromosome) genes to give a variety of phenotypes, where one gene masks the expression of another gene locus.

    It's not inherited and it reduces phenotypic variation.

    There are two types,
    Complementary
    Antagonistic

    There are then two types of antagonistic, recessive and dominant

    Recessive - Homozygous alleles at one locus are epistatic (do the masking) The locus being masked is hypostatic. A homozygous recessive at one locus means the dominant allele at the other locus is not expressed. Example, Salvia Flower. Ratio, 9: 3: 4

    Dominant - where a dominant allele at one locus is epistatic. A dominant allele at one locus prevents the expression of the dominant allele of the other locus. Example, Summer Squash Fruit Colour. Ratio, 12: 3: 1

    Complementary - A dominant allele at each locus is required for gene expression. Homozygous recessive at any locus masks the expression of the dominant allele at the other locus.

    Precursor + First dominant gene --> Intermediate + Second dominant gene --> Pigment

    Example, Sweet Pea Flower Colour. Ratio, 9:7

    Hope this helps
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    Is heritability on our syllabus?
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    (Original post by Remarqable M)
    FANTASTIC! :p: his explanation is simple and easy to follow
    Yaay :woo: It's a shame I only just discovered him, but he covers nearly our whole syllabus. :yy:
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    (Original post by xXxBaby-BooxXx)
    I'd avoid talking about mice coat colour, as that's co-dominant, which confuses the subject a bit more.

    Epistasis is the interaction between two unlinked (not on the same chromosome) genes to give a variety of phenotypes, where one gene masks the expression of another gene locus.

    It's not inherited and it reduces phenotypic variation.

    There are two types,
    Complementary
    Antagonistic

    There are then two types of antagonistic, recessive and dominant

    Recessive - Homozygous alleles at one locus are epistatic (do the masking) The locus being masked is hypostatic. A homozygous recessive at one locus means the dominant allele at the other locus is not expressed. Example, Salvia Flower. Ratio, 9: 3: 4

    Dominant - where a dominant allele at one locus is epistatic. A dominant allele at one locus prevents the expression of the dominant allele of the other locus. Example, Summer Squash Fruit Colour. Ratio, 12: 3: 1

    Complementary - A dominant allele at each locus is required for gene expression. Homozygous recessive at any locus masks the expression of the dominant allele at the other locus.

    Precursor + First dominant gene --> Intermediate + Second dominant gene --> Pigment

    Example, Sweet Pea Flower Colour. Ratio, 9:7

    Hope this helps
    Co-dominance is when both genotypes show their phenotype. For example Blood Group.
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    OH! Just discovered this thread. Notes I have made so far for this exam I posted on this thread, but will post on here now!
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    Got a D on the F214 paper... yeah I know, pretty bad! Gonna resit it! Wanted to ask you guys, how do you revise... because clearly my revision is not going right for biology and need some tips?
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    (Original post by student92)
    Got a D on the F214 paper... yeah I know, pretty bad! Gonna resit it! Wanted to ask you guys, how do you revise... because clearly my revision is not going right for biology and need some tips?
    Got a C although i was pretty confident on getting A meh... resitting it again.Find it funny as i remember about 85% of the f214 stuff .... well i guess you could start off by doing past paper.
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    (Original post by student92)
    OH! Just discovered this thread. Notes I have made so far for this exam I posted on this thread, but will post on here now!
    gOOD
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    (Original post by ibysaiyan)
    Got a C although i was pretty confident on getting A meh... resitting it again.Find it funny as i remember about 85% of the f214 stuff .... well i guess you could start off by doing past paper.
    as if you got a C, that paper was hard though, i was like 2 marks off a C. Yeah, I like knew everything in that unit... its just my exam technique, don't think I understand the question very well - i just write anything down!
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    (Original post by student92)
    as if you got a C, that paper was hard though, i was like 2 marks off a C. Yeah, I like knew everything in that unit... its just my exam technique, don't think I understand the question very well - i just write anything down!
    yep yep lol you're not the only one ... join the club.
    edit: I would've posted stuff on f215 by now but its fp2 which is sucking away my time ;p its darn hard... nothing compare to it.
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    (Original post by ibysaiyan)
    yep yep lol you're not the only one ... join the club.
    edit: I would've posted stuff on f215 by now but its fp2 which is sucking away my time ;p its darn hard... nothing compare to it.
    thats a maths exam right... not really sure as I'm on AQA for maths... Are you doing OCR Chem too?
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    (Original post by student92)
    thats a maths exam right... not really sure as I'm on AQA for maths... Are you doing OCR Chem too?
    AQA maths too... ex-chem OCR :s
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    (Original post by ibysaiyan)
    AQA maths too... ex-chem OCR :s
    Ahh right, well I've got 6 exams this summer and I'm actually terrified! ARGH! :P
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    (Original post by ibysaiyan)
    Co-dominance is when both genotypes show their phenotype. For example Blood Group.
    Oh I know what co-dominance is, I was just saying that it confuses epistasis somewhat, and as we were explaining it to someone who was struggling with the whole concept, I didn't think it wise to add another factor into epistasis.
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    (Original post by student92)
    Ahh right, well I've got 6 exams this summer and I'm actually terrified! ARGH! :P
    12 here no joke.With that said i am off early tonight i haven't done much yet.See you all later( i might wake up early lol).Oh btw. to all proxy users check http://www.proxyug.com
    Any bugs lemme know ^.^
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    (Original post by ibysaiyan)
    12 here no joke.With that said i am off early tonight i haven't done much yet.See you all later( i might wake up early lol).Oh btw. to all proxy users check http://www.proxyug.com
    Any bugs lemme know ^.^
    12 wow! Good luck x
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    so ,here's where evreybodys been ,and i thought you'll gave up on biology (i know am about to)
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    Meiosis I on this thread

    Meiosis II

    Prophase II
    - Centrioles replicate, go to opposite poles of the cell - right angles to those in Meiosis I.
    - Nuclear envelope breaks down.

    Metaphase II
    - Chromosome align on the equator of the cell with chromatids randomly arranged.
    - Microtubules attach to the centromeres.

    Anaphase II
    - Centromeres divide.
    - Sister chromatids go to opposite poles of the cell.
    - Chromatids randomly segregate.

    Telophase II
    - Nuclear membrane reforms.
    - Animals - 4 haploid daughter cells produced.
    - Plants - a tetrad of 4 haploid cells produced.


 
 
 
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