Biology · Evolution · NEET
No. A gene pool is the whole collection — all the genes and all their alleles present in a population. Allele frequency is a number that comes out of that gene pool. It tells you what fraction of a particular locus is made of one allele (for example, allele A). So the gene pool is the container, and allele frequency is a measurement taken from it.
It is a fraction (a proportion between 0 and 1), not a raw count. If a population has 100 copies of a gene and 40 of them are allele A, the frequency of A is 40/100 = 0.4, not 40. This is why NCERT writes frequencies as p, q etc., and why they can be squared (p², q²) in the Hardy-Weinberg equation.
For NEET, treat them as the same. NCERT uses the phrase 'frequency of occurrence of alleles of a gene' and often just says gene/allele frequency. Strictly, 'allele frequency' is the more correct term because we measure how common each allele (A or a) is, but the exam does not separate the two.
Because at one gene locus, every copy must be one of the possible alleles — there is no leftover. If only two alleles A and a exist, then frequency of A + frequency of a = 1, i.e. p + q = 1. NCERT states this directly: 'Sum total of all the allelic frequencies is 1.'
For the whole population. One individual only carries two alleles per locus. A gene pool is the sum of alleles across all individuals of the population, which is why allele frequencies are population-level ideas and are central to studying evolution.
Yes — a constant gene pool means allele frequencies are not changing, which is genetic equilibrium (Hardy-Weinberg equilibrium). Evolution is defined as a change in allele frequency. So if the gene pool stays constant, there is no evolution at that locus. This exact point was tested in NEET 2024.
Which of the following factors will not affect the Hardy-Weinberg equilibrium?
A gene locus has two alleles A, a. If the frequency of dominant allele A is 0.4, then what will be the frequency of homozygous dominant, heterozygous and homozygous recessive individuals in the population?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A gene pool is the total set of all genes and all their alleles found in every individual of a population. It is a population-level idea, not for a single organism.
Allele frequency is the proportion (a fraction between 0 and 1) of a particular allele at a gene locus in the gene pool. For example, if A makes up 0.4 of the copies, its frequency is 0.4.
When a locus has two alleles A and a, p is the frequency of A and q is the frequency of a. Since every copy is one of the two, they must add to 1, so p + q = 1.
Genetic equilibrium (Hardy-Weinberg equilibrium) is when allele frequencies stay constant from generation to generation, so the gene pool does not change and no evolution occurs at that locus.
Evolution is defined as a change in allele frequency in a population over generations. So when the gene pool changes (allele frequencies shift), that change is interpreted as evolution.
