Final answer:
The nonrandom association between genotypes at two loci on a chromosome is known as linkage, occurring when alleles are close together on the same chromosome and hence more likely to be inherited together.
Step-by-step explanation:
When there is a nonrandom association between the genotypes at two loci on a chromosome, the loci are said to be in linkage. This linkage phenomenon occurs because alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited together during meiosis. To illustrate this, let's consider a dihybrid cross involving flower color and plant height where the genes for these traits are next to each other on the chromosome. The alleles for tall plants and red flowers will remain together in the formation of gametes, as will the alleles for short plants and yellow flowers, demonstrating parental genotypes. The classical Mendelian prediction of a 9:3:3:1 outcome of a dihybrid cross does not apply here because of the linkage of genes. As genes move further apart on a chromosome, the odds of crossovers between them increase, and recombinant gametes appear with nonparental genotypes, allowing genes to behave more independently.