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22 September, 14:46

In a population of lizards, the allele that causes red eyes (R) is dominant, while the allele that causes green eyes is recessive (r). If 72% of the lizards have red eyes, what is the frequency of the dominant allele?

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  1. 22 September, 14:48
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    I'm not sure but it would be 72 or 0.72
  2. 22 September, 15:14
    0
    The answer is 0.47 or 47%.

    Let's first distinguish some terms and their frequencies.

    R - the dominant allele that causes red eyes

    r - the recessive allele that causes green eyes

    Since R is dominant over r, lizards with at least one dominant R allele will have red eyes. Therefore, the genotypes and the phenotypes are as following:

    genotypes - phenotypes

    RR - the lizards with red eyes

    Rr - the lizards with red eyes

    rr - the lizards with green eyes

    Now, we will use some Hardy-Weinberg equations:

    p + q = 1

    p² + 2pq + q² = 1

    where:

    p - the frequency of dominant allele R

    q - the frequency of recessive allele r

    p² - the frequency of lizards with genotype RR

    2pq - the frequency of lizards with genotype Rr

    q² - the frequency of lizards with genotype rr

    We are interested in the frequency p of the dominant R allele.

    So, we have the frequency (72%) of the lizards that have red eyes. However, lizards with genotypes RR and Rr will have red eyes. Since their frequencies are p² and 2pq, respectively, we have:

    p² and 2pq = 72% = 72/100 = 0.72

    Now, use this in the equation p² + 2pq + q² = 1:

    0.72 + q² = 1

    q² = 1 - 0.72 = 0.28

    From here, we will calculate q and later p using the formula p + q = 1:

    q² = 0.28

    q = √0.28 = 0.53

    p + q = 1

    p + 0.53 = 1

    p = 1 - 0.53

    p = 0.47
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