Question

Suppose that allele A is dominant to allele a, that genotypes AA and Aa produce phenotype B, and that genotype aa produces

phenotype C
If the frequency of allele A in a certain population is 0.6 (or 60%) and the frequency of allele a is 0.4 (or 40%), estimate the
frequencies of genotypes AA, AA, and aa. Then, determine the frequencies of phenotypes B and C.
The frequency of genotype AA is about
The frequency of genotype Aa is about
The frequency of genotype aa is about
The frequency of phenotype B is about
The frequency of phenotype C is about
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Answer 1

Answers:

The frequency of genotype AA is about 0.36

The frequency of genotype Aa is about 0.48

The frequency of genotype aa is about 0.16

The frequency of phenotype B is about 0.84

The frequency of phenotype C is about 0.16

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Step-by-step explanation:

Allele A is 60% of the population, so the chance of getting one of them is 60% or 0.60. Getting two of them in a row is a probability of 0.60*0.60 = 0.36 = 36%

The allele a's frequency is 0.4. Getting A then a would have a frequency of 0.6*0.4 = 0.24. Since Aa is the same as aA, we basically need to double 0.24 to get 0.48 to account for both scenarios of this genotype.

Getting two 'a's in a row would yield 0.4*0.4 = 0.16

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Phenotype B occurs when the genotype is AA or Aa

So the probability of this happening is 0.36+0.48 = 0.84

You just add the probabilities of genotypes AA and Aa as calculated in the section above.

The probability of phenotype C is the complement of phenotype B's probability, so 1-0.84= 0.16 are the chances of randomly getting phenotype C. Note that this is the same as the probability of getting genotype aa, as this genotype directly corresponds to the phenotype C.

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Side note: it might help to make a dihybrid cross to visually keep track of all the frequencies.