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Anales de la Facultad de Medicina

On-line version ISSN 2301-1254

Abstract

LAMOLLE, Guillermo  and  MUSTO, Héctor. Genoma Humano. Aspectos estructurales. Anfamed [online]. 2018, vol.5, n.2, pp.12-28. ISSN 2301-1254.  http://dx.doi.org/10.25184/anfamed2018v5n2a10.

The human genome, as the genome of all mammals and birds, are mosaic of isochores, which are very long streches (>> 100 kb) of DNA that are homogeneous in base composition. Isochores can be divided in a small number of families that cover a broad range of GC levels (GC is the molar ratio of guanine+cytosine in DNA). In the human genome, we find five families, which are (going from GC- poor to GC- rich) L1, L2, H1, H2 and H3. This organization has important consequences, as is the case of the concentration of genes, their regulation, transcription levels, rate of recombination, time of replication, etc. Furthermore, the existence of isochores has as a consequence the so called “compositional correlations”, which means that as long as sequences are placed in different families of isochores, all of their regions (exons and their three codon positions, introns, etc.) change their GC content, and as a consequence, both codon and amino acids usage change in each isochore family. Finally, we discuss the origin of isochores within an evolutioary framework.

Keywords : Human Genome; Isochores; Compositional Correlations; GC Content; Evolution.

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