Final answer:
Genetic map distances are not based on direct analysis of DNA. Physical maps provide detailed information about the actual physical distance between genetic markers. Three methods used to create physical maps are cytogenetic mapping, radiation hybrid mapping, and sequence mapping.
Step-by-step explanation:
Genetic map distances are not based on direct analysis of DNA.
They are based on recombination frequencies during meiosis, which estimate the distance between genes and genetic markers.
Physical maps, on the other hand, provide detailed information about the actual physical distance between genetic markers, including the number of nucleotides.
There are three methods used to create physical maps: cytogenetic mapping, radiation hybrid mapping, and sequence mapping.