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    Hi all,
    This question has got me a little puzzled.For the first cross why can't I use heterozygous alleles for the red eyed female.On the MS it shows Homozygous and down the bottom there's a note given which says If I chose hetero for cross one then correct F2 phenotypes must be chosen.
    Thanks for your help in advance. =]
    Question:
    http://img192.imageshack.us/i/capturekc.png/
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    (Original post by ibysaiyan)
    Hi all,
    This question has got me a little puzzled.For the first cross why can't I use heterozygous alleles for the red eyed female.On the MS it shows Homozygous and down the bottom there's a note given which says If I chose hetero for cross one then correct F2 phenotypes must be chosen.
    Thanks for your help in advance. =]
    Question:
    http://img192.imageshack.us/i/capturekc.png/
    For the first question, the 1:2:1 ratio required is only achieved if you cross a heterozygous red female. With a homozygous female you end up with a ratio of 1:1 (red female:red male) which doesn't match the results given.
    So basically the mark scheme sounds wrong...
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    (Original post by ibysaiyan)
    Hi all,
    This question has got me a little puzzled.For the first cross why can't I use heterozygous alleles for the red eyed female.On the MS it shows Homozygous and down the bottom there's a note given which says If I chose hetero for cross one then correct F2 phenotypes must be chosen.
    Thanks for your help in advance. =]
    Question:
    http://img192.imageshack.us/i/capturekc.png/
    You can use heterozygous alleles it just states that if you use homozygous allelles you must choose the right phenotypes for the second cross.

    Your crosses should look something like this:
    Attached Images
     
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    (Original post by kbountra)
    For the first question, the 1:2:1 ratio required is only achieved if you cross a heterozygous red female. With a homozygous female you end up with a ratio of 1:1 (red female:red male) which doesn't match the results given.
    So basically the mark scheme sounds wrong...

    Thats wrong: you get a 1:1 ratio for the f1 generation and then cross these to get the f2 generation with the correct ratio of 1:2:1. Meaning you can use either a homozygous or heterozygous female for the first cross you jusr have to be careful which ones you choose for the second cross.

    Like this:
    Attached Images
     
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    (Original post by Kedix)
    Thats wrong: you get a 1:1 ratio for the f1 generation and then cross these to get the f2 generation with the correct ratio of 1:2:1. Meaning you can use either a homozygous or heterozygous female for the first cross you jusr have to be careful which ones you choose for the second cross.

    Like this:
    Yep my bad- can't believe I missed out doing the F2 generation...not good for a prospective biochemist.
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    (Original post by kbountra)
    Yep my bad- can't believe I missed out doing the F2 generation...not good for a prospective biochemist.
    It's an easy mistake to make as you can't see half of the question
 
 
 
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