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Calculate how frequently we expect to observe each possible genotype identified in problem 1. Please show your work. Refer to the outline you developed or reread the preceding sections for guidance.
The frequency with which a genotype will occur in the offspring generation is equal to the multiplicative product of the frequency with which each allele comprising the genotype appears in the parent generation.
Counting the buckets depicted in Figure 1 above reveals that the A allele occurs with a frequency equal to 15 out of 20 or 0.75 and the a with a frequency equal to 5 out of 20 or 0.25 in the parental generation. Consequently,
Now check your work: have you identified every possible genotype that could appear in the offspring generation when each parent has an equal chance of reproducing in the population above?
To do this, consider the following: if we have identified every possible genotype, then the frequencies calculated in question 2 will sum to 1 (i.e. 100%) because we will have accounted for 100% of the genotypes that could possibly occur in the offspring if all parents have an equal chance of reproducing and contributing alleles to the next generation.
Check your work. Have you omitted any possible offspring genotypes? How do you know? Please explain.
We have not omitted any possible genotypes because the expected genotype frequencies (0.5625 + 0.0625 + 0.375) sum to 1 as expected if we have accounted for every possible genotype that could occur in the offspring generation of a randomly mating, parental generation with these allele frequencies.
If you have missed a genotype, what one do you think you have missed? Why?
If you missed one genotype, it was probably a heterozygote, either Aa or aA . Review the information found here to understand the likely source of your error.
If you have missed one, correct your response to question 2 above. Now you should have an accurate description of the offspring genotype frequencies that will materialize when every parent has an equal chance of reproducing in this population.
Finally, we are ready to address the question heading this module, are offspring generation genotype frequencies necessarily expected to be the same as parental generation genotype frequencies when every parent has an equal chance of surviving and reproducing? Please explain using your results to support your conclusion.
No, parental and offspring generation genotype frequencies will not necessarily be the same in a population that is not evolving. Our data support this conclusion because in the parental generation above, the AA , aa , and Aa genotypes occur with frequencies equal to 5 out of 10 or 0.5, 0 out of 10 or 0.0 and 5 out of 10 or 0.5, respectively. Whereas, if these parents mate randomly, the AA , aa , and Aa genotypes will occur in their offspring with frequencies equal to 0.5625, 0.0625 and 0.375 respectively.
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