Punnett Square Problem ?

Discussion in 'Pre-Medical - MD' started by FreeMeDoctor, Apr 7, 2007.

  1. FreeMeDoctor

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    If you start out with two pure breeing parents and cross them to get an F1 generation then self-cross the F1 generation with itself ( self-cross ) then cross the F2 with themselves ( self the F2 gen ) you will 3:1 ratio of the dominant phenotype in the F3 generation.

    Can anyone show me how to do the punnett square for the selfing of the F2 generation ? The thing I dont understand is how to do a punnett square when there are three different gamete combinations being crossed. This seems impossible to me.

    Thank you for your help.
     
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  3. StritchMD2011

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    This isn't a homework help forum.
     
  4. Sol Rosenberg

    Sol Rosenberg Long Live the New Flesh!
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    You mean gametes with three different traits (trihybrid cross)? The Punnett square has 64 (4 x 16) entries, and is best done as a branch diagram (i.e. don't do all 64 combinations explicitly like in a Punnett square) but is not impossible. I'm sure there's an example in your Genetics book or online somewhere.
     

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