Recombination Frequency

Recombination frequency measures how often two genes are separated by crossing over during meiosis, so it estimates how far apart they are on a chromosome. If two loci are close together, crossover between them is rare and few recombinant offspring appear; if they are farther apart, recombinants are more common. Because 1% recombination is defined as 1 map unit, the result is also used as an approximate genetic distance in centimorgans, although it can underestimate very large distances when multiple crossovers occur.

Use this when analyzing offspring from a testcross or other genetic cross to infer linkage and estimate map distance between two genes. It is especially useful in classical genetics, linkage mapping, and problems asking whether genes assort independently or are linked.

• Counting only one recombinant class instead of adding all recombinant offspring together
• Using the number of parental offspring in the numerator instead of the recombinant offspring
• Treating recombination frequency as exact physical distance even though double crossovers can make the map distance an underestimate