Final answer:
True, a population with genotypic frequencies different from 1:2:1 indicates that it is not in Hardy-Weinberg Equilibrium, suggesting the influence of evolutionary forces.
Step-by-step explanation:
The statement "A population with genotypic frequencies different from 1:2:1 cannot be at Hardy-Weinberg Equilibrium" is true.
The Hardy-Weinberg principle provides a mathematical baseline whereby a population's allele and genotype frequencies are inherently stable—meaning in the absence of evolutionary forces such as mutation, natural selection, genetic drift, gene flow (migration), and nonrandom mating—expected genotype frequencies for a two-allele system are in the proportions p²:2pq:q² (where p and q are the frequencies of the respective alleles). These proportions translate to the 1:2:1 ratio when allele frequencies are equal (p = q = 0.5). If observed genotypic frequencies do not align with the expected values according to the Hardy-Weinberg formula, scientists can infer that one or more of the evolutionary forces are in play, indicating that the population is not in equilibrium and is thus evolving.