The concepts of gene pool and allele frequency
A gene pool is every allele (version of a gene) that exists across all individuals in a population. Allele frequency measures how common each allele is within that pool.
Formula
Allele frequency = (number of copies of that allele) / (total number of all alleles at that locus)
Real World
The sickle-cell allele (HbS) has a frequency of around 0.12 in parts of West Africa because carriers gain partial resistance to Plasmodium falciparum malaria, keeping the allele common in the gene pool.
Exam Focus
Remember allele frequency refers to the population, not an individual — always express it as a decimal between 0 and 1, not as a genotype.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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