Anonymous
Anonymous asked in Science & MathematicsBiology · 1 decade ago

Frequency in Population?

Pink flowers are Homozygous dominant and White flowers are homozygous recessive. In 2009 white flowers comprised 8% of a population. What is the frequency of the homozygous dominant and heterozygous in this population?

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  • 1 decade ago
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    You would want to use the Hardy-Weinberg Law for calculating this.

    p^2+2pq+q^2=1

    where

    p^2=frequency of AA (homozygous dominant) in population

    2pq=frequency of Aa (heterozygous) in population

    q^2=frequency of aa (homozygous recessive) in population

    Since q^2 is the aa in population (the white flowers) we know that q^2=8%, or q^2=0.08.

    This would make q=0.2828.

    You then have p^2+2p(0.2828)+(0.2828)^2=1

    p^2+0.5656p+0.08=1

    p^2+0.5656p-0.92=0

    This leaves you with a quadratic, which when solved gives you p=0.7172

    (I cheated on this step and used a quadratic equation solving app)

    Now to solve for p^2 and 2pq

    p^2=0.7172^2=0.514, or 51.4%

    2pq=2*0.7172*0.2828=0.406 or 40.6%

    So, you have

    =51.4% AA (Homozygous dominant, pink flowers)

    =40.6% Aa (Heterozygous, pink flowers)

    To check, you can make sure that, with the 8% Homozygous recessive, this adds up to 100%

    ....

    Or you could completely cheat and use this Hardy-Weinberg Calculator.

    http://www.changbioscience.com/genetics/hardy.html

    It's at least helpful for checking your answers if you need to show work.

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  • Anonymous
    1 decade ago

    You're looking for the Hardy-Weinberg formula here:

    p^2 + 2pq + q^2 = 1

    You've been told that the homozygous recessives (p^2) are 8% (0.08). With this number, you can work out what p must be.

    Then, do the maths.

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