Final answer:
The incorrect statement about a population in linkage equilibrium is that 'The disequilibrium constant D is equal to its minimum value of -0.25.' Linkage equilibrium suggests allele frequencies at different loci do not affect one another, and D can vary from -0.25 to 0.25, not remain fixed at its minimum value.
Step-by-step explanation:
Direct answer in 2 lines: The statement that is NOT true when a population is in linkage equilibrium is that 'The disequilibrium constant D is equal to its minimum value of -0.25.'
Explanation in 200 words: Linkage equilibrium, also related to the Hardy-Weinberg equilibrium, suggests that the allele frequencies at different loci are independent of one another. This means the frequency of one allele on a chromosome does not affect the frequency of another allele at a different locus on that same chromosome. If we're in linkage equilibrium, the frequency of a haplotype (combination of alleles at different loci) can indeed be calculated by multiplying the frequencies of the individual alleles of the loci in question. Moreover, the frequency of allele B being on chromosomes with allele A would be the same as the frequency of B on chromosomes with allele a, assuming random mating and no evolutionary forces at play.
However, the disequilibrium constant D, which measures the non-random association between alleles at different loci, does not necessarily have to be at its minimum value of -0.25 in a population in equilibrium. D can vary in a range from -0.25 to 0.25 depending on the frequencies of the alleles. Therefore, the option stating that D equals -0.25 implies a specific degree of disequilibrium, which is not representative of the general case of linkage equilibrium.