Linkage

Linkage is the property of being connected or associated, and the term is used across fields to describe relationships that affect inheritance, function, or the integration of parts. It often refers to patterns of connection that influence how traits, components, or signals are transmitted or combined.

In genetics, genetic linkage refers to the tendency of genes that lie close to one another on the same chromosome to be inherited together during meiosis. Linked genes do not assort independently, in contrast to the patterns described by Mendel for unlinked loci. Recombination during crossing over can break linkage, creating new allele combinations. The strength of linkage is measured by recombination frequency, expressed in centimorgans (cM), where 1% recombination equals 1 cM. Linkage maps place genes along chromosomes and estimate their relative distances. In population genetics, linkage disequilibrium describes non-random associations of alleles at different loci within a population and is used in mapping disease genes. Statistical methods, such as LOD (logarithm of odds) scores and multipoint analyses, assess evidence for linkage between loci and traits.

In mechanical engineering, a linkage is an assembly of rigid bars connected by joints to form a mechanism that transmits motion and force. Common configurations include four-bar linkages and slider-crank mechanisms, which convert input motion into output motion with defined displacement characteristics. Linkages are fundamental in engines, robotics, and automation, enabling controlled movement and the transfer of power.

In computing, linkage describes how software components are connected, including static linking of libraries at compile time and dynamic linking that binds at run time, with implications for program size, startup time, and dependency management.