Mechanisms of genome expansion

There are several mechanisms via which a genome can expand:

- Duplication of either all or part of the genome via polyploidy.
- Unequal recombination and/or non-reciprocal translocations.
- Amplification of retrotransposable elements. These are DNA sequences which replicate autonomously. The original copy remains in place, while the new copies are inserted elsewhere in the genome.

Cultivated wheat is either tetraploid (twice the wild type chromosome number) or hexaploid (triple the wild type chromosome number). Many other crop species are polyploid, including cotton (4x), oat (6x), canola (4x), potato (4x), banana (3x), sugar cane (16x) etc.