Chromosomal rearrangement

This instability is usually due to the propensity of these regions to misalign during DNA repair, exacerbated by defects of the appearance of replication proteins (like FEN1 or Pol δ) that ubiquitously affect the integrity of the genome.

[citation needed] Heng[6] and Gorelick and Heng[7] reviewed evidence that sexual reproduction helps preserve species identity by acting as a coarse filter, weeding out chromosomal rearrangements, but permitting minor variation, such as changes at the nucleotide or gene level (that are often neutral) to pass through the sexual sieve.

[8] It is possible that speciation frequently occurs when a population becomes fixed for one or more chromosomal rearrangements that reduce fitness when they are heterozygous.

This theory is lacking in theoretical support because mutations that cause a large reduction in fitness can only be fixed through genetic drift in small, inbred populations, and the effects of chromosomal rearrangements on fitness are unpredictable and vary greatly in plant and animal species.

[9] Exemplifying (extensive) chromosome rearrangements can be found in the complete and haplotype-resolved African cassava (TME204) genome that was reconstructed and made available using the Hi-C technology.

Schematic karyogram , with annotated bands and sub-bands as used in the International System for Human Cytogenomic Nomenclature of chromosomal rearrangements. It shows 22 homologous autosomal chromosome pairs, both the female (XX) and male (XY) versions of the two sex chromosomes , as well as the mitochondrial genome (at bottom left).