Which one of the following facts is not true about genetic equilibriu…

The correct answer is Option (1) → Allelic frequencies in a population change from generation to generation

Option (1) Allelic frequencies in a population change from generation to generation — Not true of genetic equilibrium. In equilibrium they stay constant; change means evolution.

Option (2) The sum total of all allelic frequencies is 1 — True of genetic equilibrium. p + q = 1, so p² + 2pq + q² = 1.

Option (3) Allelic frequencies in a population are stable — True of genetic equilibrium. This is what equilibrium means: the allele frequencies stay the same from one generation to the next.

Option (4) Mutation and natural selection can change genetic equilibrium — True of genetic equilibrium. Both are among the five factors that disturb it.

NCERT Extract:
Hardy-Weinberg Principle – “In a given population one can find out the frequency of occurrence of alleles of a gene or a locus. This frequency is supposed to remain fixed and even remain the same through generations. Hardy-Weinberg principle stated it using algebraic equations. This principle says that allele frequencies in a population are stable and is constant from generation to generation. The gene pool (total genes and their alleles in a population) remains a constant. This is called genetic equilibrium. Sum total of all the allelic frequencies is 1.”