What is "isochore"

n. 1 (context physics English) A line drawn on a pressure / volume / temperature graph through all points having the same value of the volume 2 (context geology English) A contour showing points of equal vertical thickness of strata; equal to an isopach if strata are horizontal 3 (context genetics English) A sequence of DNA that has a reasonably constant proportion of pairs of guanine and cytosine bases, and is rich in genes

Isochore may refer to:

• an Isochoric process in thermodynamics
• isochore (genetics)
• isochore map ( geology)

In genetics, an isochore is a large region of DNA (greater than 300 kb) with a high degree uniformity in guanine (G) and cytosine (C): G- C and C-G (collectively GC content).

Bernardi and colleagues first uncovered the compositional non-uniformity within vertebrate genomes using thermal melting and density gradient centrifugation. The DNA fragments extracted by the gradient centrifugation were later termed "isochores", which was subsequently defined as "very long (much greater than 200 KB) DNA segments" that "are fairly homogeneous in base composition and belong to a small number of major classes distinguished by differences in guanine-cytosine (GC) content". Subsequently, the isochores "grew" and were claimed to be ">300 kb in size." The theory proposed that isochore’s composition varied markedly between "warm-blooded" (homeotherm) vertebrates and "cold-blooded" (poikilotherm) vertebrates and later became known as the isochore theory.