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DAT Destroyer Biology Question 185

Discussion in 'DAT Discussions' started by mkhan27, Sep 24, 2014.

  1. mkhan27

    mkhan27 5+ Year Member

    331
    80
    Mar 18, 2011
    A dihybrid cross was done between tall round peas. Tall is dominant to short and round is dominant to wrinkled. What fraction of the offspring will be short and wrinkled.

    a) 1/16
    b) 3/16
    c) 6/16
    d) 9/16
    e) None of these.

    Answer is A. I get how they got it based on the 9:3:3:1 ratio for these types of crosses, but.........am I overthinking here? The question says a dihybrid cross was done between tall round peas, but it doesn't say that it was a heterozygous dihybrid cross (i.e. TtRr). Tall round can also mean TTRR or TtRR or TTRr. My question is: Is a dihybrid cross by default with a TtRr x TtRr (unless they specify something like "A homozygous dominant tall and heterozygous wrinkled pea is crossed with a heterozygous tall and heterozygous round pea")
     
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  3. pilotdentist

    pilotdentist 2+ Year Member

    200
    54
    Feb 26, 2014
    Columbus, OH
    Its a "dihybrid", which implies heterozygous. If you hear dihybrid cross, i would assume its heterozygous and us 9331.
     
  4. mkhan27

    mkhan27 5+ Year Member

    331
    80
    Mar 18, 2011
    Thanks
     

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