Centimorgan
A centimorgan (cM) measures genetic distance, showing 1% chance of two loci separating during meiosis. It's not physical length but linkage frequency, key for ancestry and gene mapping.
A centimorgan (cM) is a unit of genetic distance used in genetics, representing 1% of the probability that two loci will be separated during meiosis. It is not a measure of physical length but of linkage frequency, and its scope covers gene mapping, ancestry testing, and evolutionary studies. The term originates from Thomas Hunt Morgan's work on genetic linkage in the early 20th century.
What this means in real life
If a gene for eye color and a gene for hair texture are 10 centimorgans apart, there's roughly a 10% chance a child inherits them separately rather than together from a parent.
What it isn’t
It is not a physical measurement of chromosome length—two markers 1 centimorgan apart may be vastly different distances in actual DNA base pairs, depending on local recombination rates.
Commonly misused online
Often conflated with physical distance on DNA; people assume 1 centimorgan always equals the same number of base pairs, when recombination rates vary across the genome.