Q.State the Hardy-Weinberg principle. Derive the equation $p^2 + 2pq + q^2 = 1$ for a gene with two alleles, $A$ (frequency $p$) and $a$ (frequency $q$), present in a population.

Genetic equilibrium requires the absence of mutation (along with several other conditions), since mutation is one of the forces that changes allele frequencies.

The Hardy-Weinberg principle states that allele frequencies remain constant (in equilibrium) across generations only if a population is large, mates randomly, and is free from mutation, natural selection, migration (gene flow), and genetic drift. Among the given options, 'No mutation' is the essential condition listed for maintaining equilibrium, since mutation actively introduces new alleles or changes existing ones, thereby altering allele frequencies. Genetic drift (b) and gene flow (c) are themselves disturbing factors (not conditions for equilibrium) that change allele frequencies, especially in small populations or through migration, and genetic recombination (d) reshuffles existing alleles into new combinations but does not by itself change their overall frequency in the gene pool the way mutation does.

The Hardy-Weinberg principle holds when allele frequencies stay constant; it is disturbed by gene flow, genetic drift, mutation, migration, genetic recombination and natural selection. Recapitulation (a discredited embryological theory) is not one of these factors.

The Hardy-Weinberg principle states that allele and genotype frequencies (p² + 2pq + q² = 1) remain constant across generations in an ideal population. Equilibrium is disturbed by five/six evolutionary agencies: gene migration (gene flow), genetic drift, mutation, genetic recombination, and natural selection.

Given options a (gene flow), b (mutation) and c (migration) all disturb the equilibrium. Recapitulation ("ontogeny recapitulates phylogeny") is an embryological hypothesis about developmental stages — it has nothing to do with changing allele frequencies. Hence it does not affect the Hardy-Weinberg principle.

A standard NCERT/CBSE Class 12 Biology Evolution board question.

In a Hardy-Weinberg equilibrium population, the frequency of heterozygotes (Aa) is given by 2pq, which here equals 0.48.

A change in gene (allele) frequency occurring purely by chance is called genetic drift.

Gene migration is the transfer of alleles between populations through the movement of individuals, which alters the allele frequencies of the populations involved.

According to the Hardy-Weinberg principle, allele and genotype frequencies in a population remain constant (in equilibrium) generation after generation, provided certain conditions hold — no mutation, random mating, no natural selection, a large population size, and no gene migration. Gene migration (gene flow) is one of the factors that disturbs this equilibrium: when individuals move from one population into another (immigration) or leave a population (emigration), they carry their alleles with them. This changes the allele frequencies of both the population they leave and the population they join. If gene migration continues over generations between two populations, it tends to make the allele frequencies of the two populations more similar to each other, counteracting local differentiation caused by selection or drift.

The Hardy-Weinberg principle allows us to calculate genotype frequencies from allele frequencies in a stable population. Given the dominant allele frequency p = 0.6, the frequency of the heterozygous genotype 'Aa' is 0.48.

The founder effect is genetic drift in a small colonising group whose original drifted members become the founders of the new population.

The Hardy-Weinberg principle states that allele and genotype frequencies in a population remain constant (in equilibrium) generation after generation, in the absence of evolutionary forces.

According to the Hardy-Weinberg principle, allele frequencies in a population are stable/constant and remain in equilibrium from one generation to the next, provided the population is large, mating is random, and there is no mutation, migration, selection, or genetic drift. Summed allele frequencies always equal 1 (p + q = 1), and expected genotype frequencies follow p² + 2pq + q² = 1. Deviation from these expected frequencies indicates evolution is occurring.

Selective (non-random) mating violates one of the core assumptions of Hardy-Weinberg equilibrium, so the population will not remain in equilibrium.

The Hardy-Weinberg principle holds that allele and genotype frequencies in a population remain constant across generations only if several conditions are met: a very large population size (no genetic drift), no migration (gene flow) in or out, no mutation, random mating, and no natural selection acting on the alleles. Options (a) no migration, (c) large population, and (d) no mutations are all conditions that HELP maintain equilibrium, so they are not the answer. Selective (non-random) mating (b), however, means individuals preferentially choose mates based on certain traits/genotypes rather than mating randomly, which changes genotype frequencies (though not necessarily allele frequencies directly) and is one of the classic factors -- alongside mutation, migration, genetic drift and natural selection -- that disturbs Hardy-Weinberg equilibrium.

Non-random (selective) mating is one of the classic factors that disrupts Hardy-Weinberg equilibrium.

The Hardy-Weinberg principle predicts that allele and genotype frequencies in a population remain constant across generations only if several idealised conditions hold: a very large population size (to avoid genetic drift), no mutation, no migration (gene flow), no natural selection, and random mating. If individuals mate selectively -- choosing mates based on particular traits rather than at random -- genotype frequencies shift away from Hardy-Weinberg expectations even without any change in allele frequency itself. The other three options (a large population, no mutations, no migration) are each conditions that HELP maintain equilibrium, not deviations from it, so they are the opposite of what disrupts HWE.

(b) Gene flow — the movement of alleles/genes between genetically different populations via migration and interbreeding, one of the mechanisms driving evolutionary change.

Gene flow is the transfer of genes between populations by migration.

Gene flow (migration) occurs when individuals (or their gametes) move from one population to another and interbreed, introducing new alleles into the recipient population's gene pool and tending to reduce genetic differences between the two populations. This is distinct from gene mutation (a spontaneous change in the DNA sequence creating a new allele), genetic drift (random, chance fluctuations in allele frequency, especially significant in small populations), and genetic recombination (new allele combinations arising from crossing over/independent assortment during meiosis within one population). Gene flow is one of the key evolutionary forces that can change allele frequencies and counteract the genetic divergence between populations caused by natural selection or drift.

The sum total of genes/alleles in an interbreeding population is termed the gene pool.

The gene pool represents all the alleles of all genes carried by every individual in a population capable of interbreeding, and its allele frequencies form the basis for studying evolutionary change (e.g., via the Hardy-Weinberg principle). Changes in gene-pool composition over generations, due to mutation, selection, migration or genetic drift, constitute evolution at the population level. 'Genome' instead refers to the complete set of genes/DNA of a single organism or species, not a population; 'gene accumulation' and 'gene population' are not standard genetics terms.