Editing Polyploidy (section)

=== Temporal terms ===

==== Neopolyploidy ====
A polyploid that is newly formed.

==== Mesopolyploidy ====
That has become polyploid in more recent history; it is not as new as a neopolyploid and not as old as a paleopolyploid. It is a middle aged polyploid. Often this refers to whole genome duplication followed by intermediate levels of diploidization.

==== Paleopolyploidy ====
[[File:PaleopolyploidyTree.jpg|upright=1.5|thumb|This [[phylogenetic tree]] shows the relationship between the best-documented instances of [[paleopolyploidy]] in eukaryotes.]]

{{Main|Paleopolyploidy}}
Ancient genome duplications probably occurred in the evolutionary history of all life. Duplication events that occurred long ago in the history of various [[Lineage (evolution)|evolutionary lineages]] can be difficult to detect because of subsequent [[diploidization]] (such that a polyploid starts to behave cytogenetically as a diploid over time) as [[mutation]]s and gene translations gradually make one copy of each chromosome unlike the other copy. Over time, it is also common for duplicated copies of genes to accumulate mutations and become inactive pseudogenes.<ref>{{cite journal | vauthors = Edger PP, Pires JC | title = Gene and genome duplications: the impact of dosage-sensitivity on the fate of nuclear genes | journal = Chromosome Research | volume = 17 | issue = 5 | pages = 699–717 | year = 2009 | pmid = 19802709 | doi = 10.1007/s10577-009-9055-9 | doi-access = free }}</ref>

In many cases, these events can be inferred only through comparing [[DNA sequencing|sequenced genomes]]. Examples of unexpected but recently confirmed ancient genome duplications include [[baker's yeast]] (''[[Saccharomyces cerevisiae]]''), mustard weed/thale cress (''[[Arabidopsis thaliana]]''), [[rice]] (''[[Oryza sativa]]''), and two rounds of whole genome duplication (the [[2R hypothesis]]) in an early [[evolution]]ary [[ancestor]] of the [[vertebrates]] (which includes the [[human]] lineage) and another near the origin of the [[teleost]] [[fishes]].<ref name="Clarke_2016" /> [[Angiosperm]]s ([[flowering plant]]s) have paleopolyploidy in their ancestry. All [[eukaryote]]s probably have experienced a polyploidy event at some point in their evolutionary history.