Principles of The Isochore Theory
The isochore theory was the first to identify the nonuniformity of nucleotide composition within vertebrate genomes and predict that the genome of "warm-blooded" vertebrates such as mammals and birds are mosaic of isochores (Bernardi et al. 1985). The human genome, for example, was described as a mosaic of alternating low and high GC content isochores belonging to five compositional families, L1, L2, H1, H2, and H3, whose corresponding ranges of GC contents were said to be <38%, 38%-42%, 42%-47%, 47%-52%, and >52%, respectively.
The main predictions of the isochore theory are that:
- GC content of the third codon position (GC3) of protein coding genes is correlated
with the GC content of the isochores embedding the corresponding genes.
- The genome organization of warm-blooded vertebrates is a mosaic of mostly GC-rich isochores.
- Genome organization of cold-
blooded vertebrates is characterized by low GC content levels and lower compositional heterogeneity than warm-blooded vertebrates. Homogeneous domains do not reach the high GC levels attained by the genomes of warm-blooded vertebrates.
Read more about this topic: Isochore (genetics)
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