Namely, rather than all only the data passing through some central nodes are duplicated as a precaution against their malfunctioning.
However, salmonids experienced a lineage-specific WGD [ 28], and thus there is potential to have duplicates of genes that were duplicated as a result of the 3R WGD.
A follow-up study suggested that these combinations are formed once during evolution of the protein repertoire and are duplicated as a single evolutionary unit [ 5].
Surprisingly, some strains gave an amplification product and some did not, indicating that in some strains the 13-kb region was duplicated as a tandem repeat but not in others (Fig. 3A, Table 1).
The Nannochloropsis mitochondrial genomes are devoid of Clp homologs, yet all Nannochloropsis chloroplasts contain two or three (clpC2 is duplicated as a part of the IR in some species [ 12]) gene homologs of clpC, respectively.
The local duplication event could have occurred in early vertebrate evolution, whereupon the gene pair was duplicated as a unit, most likely concomitantly with Hox (i.e. in 2R).
Unlike in D. melanogaster, where A6 is duplicated as a mirror image in Kr mutants (Nüsslein-Volhard and Wieschaus, 1980; Wieschaus et al., 1984b), we cannot identify clear instances of local inversions or duplications in M. abdita.
When genes are duplicated as a consequence of polyploidization, they may continue to evolve at the same rate as they did in their diploid ancestors, or they may be subject to pressures that lead to differential rates of sequence evolution [ 2].
The entire chromosome III and two fragments from chromosomes IV and XII in a culture of budding yeast (S. cerevisiae) were duplicated as a "transient evolutionary solution" in response to high temperature - a "transition" that fostered the survival of between 400 and 2,000 generations.
