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Genomic complexity can be added, at the small or large-scale, and it can occur over cis-regulatory or coding regions. It can involve horizontal transfer from another genome or duplication of elements already present in the genome. Here, we will consider different ways to add genetic complexity and how they might affect organismal complexity. This figure focuses on duplication rather than horizontal transfer for simplicity but similar consequences can occur with horizontal transfer as well. Smaller scale duplications can occur via errors in DNA replication, errors in meiotic crossing over, or transposon insertion. Larger scale duplications can occur via errors in meiotic crossing over, transposon insertion, or whole chromosome duplication via missegregation of chromosomes during cell division. Small scale duplications can duplicate a single functional domain (like a bHLH domain), a single coding sequence, a single gene, or a single cis-regulatory protein binding site. Duplicating a gene (or at least a coding region) can have one of three major effects: creation of a pseudogene, DDS (duplication, divergence, subfunctionalization), or DDN (duplication, divergence, neofunctionalization). Pseudogenes do not add organismal complexity, but subfunctionalization and neofunctionalization potentially can. Larger-scale duplications can also occur over either cis-regulatory regions or protein-coding/gene regions.

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complexity, evolution, development, transposon, duplication, divergence, DDS, enhancer, GRN, evodevo