Final answer:
Multiple crossovers that go undetected can cause an underestimation of the true physical distances between genes when maps are based on recombination rates. Recombination frequencies are used to estimate genetic distances, but accuracy decreases with increased genetic distance and multiple crossovers can complicate these estimates.
Step-by-step explanation:
Some multiple crossovers go undetected; thus, maps based on recombination rates underestimate the true physical distances between genes. Recombination frequency is calculated by counting the offspring with nonparental genotypes. However, complex events like multiple crossoverts that are not detected can skew the estimation of genetic distances. For instance, a recombination frequency of 0.01 corresponds to 1 centimorgan (cM), and it is significant to note that as the recombination frequency approaches 0.50, mapping predictions become less accurate because it indicates that genes may be either very far apart on the same chromosome or on different chromosomes. In addition, the presence of recombination hotspots and coldspots can affect the accuracy of these maps, emphasizing the importance of employing multiple methods for mapping information. Physical maps, which utilize sequencing data, can provide more precise distances between genes.