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Allele frequencies of the next generation

  1. Oct 12, 2014 #1
    1. The problem statement, all variables and given/known data
    Starting with 75 light-colored beans and 25 dark-colored beans, the 100 beans represent my gene pool. Light beans = F and dark beans = f.
    p = (total F alleles) / (total number of beans used)

    And now I'm stuck where it's asking me to "practice determining the initial allele frequencies (p and q) for both F and F alleles, but change the top number to genotype ff x 2."

    2. Relevant equations
    Hardy-Weinberg equation = p^2 + 2pq + q^2 = 1

    3. The attempt at a solution
    I got this far:
    I have 75 light beans and 25 dark beans. Light beans = F and dark beans = f.
    Number of offspring with genotype FF (2 light beans) = 75 x 2 = 150

    Number of offspring with genotype Ff (one dark one light) = 25 x 1 = 25

    Total F alleles = 175

    I thought to find the allele frequencies of p and q in the next generation I had to square them and then do 2pq and add it, but nothing I do adds up to 1.
     
  2. jcsd
  3. Oct 12, 2014 #2

    epenguin

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    It was not very easy to make out what the question was (it would have been better to quote from your book or problem sheet) but it seems the question is nothing about the next generation but about the one you've got. You've quoted Hardy-Weinberg, which assumes genetic equilibrium so the next generation will have just the same frequencies of everything as this. I would bet it says that the dark beans are ff, doesn't make too much sense otherwise. Small letters conventionally represent recessive genes. So you re told the frequency of ff, not too difficult to work out the frequency of f.
     
  4. Oct 12, 2014 #3
    Thank you so much, turns out I was being played by my teacher. He wanted to see if we would come to this conclusion, and I over thought the whole thing. Thanks again.
     
  5. Oct 14, 2014 #4

    epenguin

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    So what is the answer?
     
  6. Oct 14, 2014 #5
    The answer is just what you said, that in Hardy-Weinberg equilibrium the allele frequency would stay the same through each generation. So basically all that work for a simple answer.
     
  7. Oct 15, 2014 #6

    epenguin

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    So the allele frequencies in next generation remain the same as for this generation (most probably, for large enough populations etc.) but the question was what are they?
     
  8. Oct 15, 2014 #7
    It was .75 for F and .25 for f.
     
  9. Oct 17, 2014 #8

    epenguin

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    I don't think so.
     
    Last edited: Oct 17, 2014
  10. Oct 20, 2014 #9
    Then what do you think it was?
     
  11. Oct 20, 2014 #10

    epenguin

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    The rule is I shouldn't answer for you. But you could not have a more classic first-lesson example of inheritance in a diploid organism with dominant/recessive genes; does a phenotype 3:1 ratio remind you of anything?
     
    Last edited: Oct 22, 2014
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