izochor

Izochor is a term that appears occasionally as a variant spelling of "isochor" or "isochore" in scientific literature. In standard genomics, an isochore (plural isochores) refers to a large region of DNA with relatively uniform base composition, especially GC content. The concept, introduced by Gian-Carlo Bernardi in the 1990s, describes how mammalian genomes are organized into long, compositionally homogeneous segments that range from hundreds of kilobases to several megabases in length. Isochores are typically categorized into GC-poor and GC-rich families, with further subdivisions (for example, L1, L2, H1, H2, H3) reflecting increasing GC content. The arrangement of isochores correlates with various genomic features, including gene density, replication timing, chromatin structure, and recombination rates, and it has informed studies of genome evolution and architecture.

In practice, "izochor" is not a standard term in modern literature and is usually encountered as a misspelling or alternate transliteration of "isochore." When encountered, it should be interpreted in the context of the isochore concept unless the source specifies a different meaning. Contemporary views recognize that GC content is best described as a spectrum rather than discrete blocks, though isochores remain a useful historical and analytical concept in comparative genomics.

See also: Isochore, Genome architecture, GC content, Gian-Carlo Bernardi, Chromosome biology