Final answer:
Distance on a chromosome is measured in centiMorgans (cM) or Map units, both representing a relative distance that corresponds to a 1% chance of recombination per generation. Recombinant units reflect the same concept but are less commonly used. Centimeters are not a measure used in genetic mapping.
Step-by-step explanation:
Distance on a chromosome is generally measured in centiMorgans, Map units, and Recombinant units. These units are utilized in the context of genetic mapping and linkage analysis. CentiMorgans (cM), also known as map units, are a relative distance that corresponds to a recombination frequency of 0.01. Thus, if we say two genes are separated by 1 cM, it implies there's a 1% chance that a recombination event will occur between them per generation. Map units are another term for centiMorgans. Recombinant units are a conceptual measurement not widely used today, but it reflects the same idea as cMs, emphasizing the recombination aspect of genetic distance. Centimeters, in this context, do not measure genetic distance and are not used for chromosome mapping. Thus, the correct choices for measuring genetic distance on a chromosome are centiMorgans, Map units, and potentially Recombinant units.