chromosomal evolution
In eukaryotes, chromosomal rearrangements, such as inversions, translocations and duplications, are common and range from part of a gene to hundreds of genes.
Lineage-specific patterns are also seen: translocations are rare in dipteran flies, and angiosperm genomes seem prone to polyploidization. In most eukaryotes, there is a strong association between rearrangement breakpoints and repeat sequences.
Some repeats promoted rearrangements via non-allelic homologous recombination, for others the association might not be causal but reflects the instability of particular genomic regions.
Rearrangement polymorphisms in eukaryotes are correlated with phenotypic differences, so are thought to confer varying fitness in different habitats.
Some seem to be under positive selection because they either trap favorable allele combinations together or alter the expression of nearby genes.
There is little evidence that chromosomal rearrangements cause speciation, but they probably intensify reproductive isolation between species that have formed by another route.
The chromosome complements (karyotypes) of animals display a great diversity in number and morphology. Against this background, the genomes of all species are remarkably conserved, not only in transcribed sequences, but also in some chromosome-specific non-coding sequences and in gene order. A close examination with chromosome painting shows that this conservation can be resolved into small numbers of large chromosomal segments. Rearrangement of these segments into different combinations explains much of the observed diversity in species karyotypes. (18007651)
References
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Robinson TJ, Ruiz-Herrera A, Froenicke L. Dissecting the mammalian genome—new insights into chromosomal evolution. Trends Genet. 2006 Jun;22(6):297-301. PMID: 16678302
Kohn M, Hogel J, Vogel W, Minich P, Kehrer-Sawatzki H, Graves JA, Hameister H. Reconstruction of a 450-My-old ancestral vertebrate protokaryotype. Trends Genet. 2006 Apr;22(4):203-10. PMID: 16517001
Coghlan A, Eichler EE, Oliver SG, Paterson AH, Stein L. Chromosome evolution in eukaryotes: a multi-kingdom perspective. Trends Genet. 2005 Dec;21(12):673-82. PMID: 16242204
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