Useful divergence

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When detecting conserved sequences between genomic regions (usually non-coding sequence), the sequences need to have been diverged for a long enough period of time so that sequences that are not under selection will have been randomized, but not for so long that detecting conservation is impossible. This means that there is a useful “window” of divergence between genomic regions for detecting conserved sequences. For example, siblings are not diverged enough and much conserved sequence is expected due to their recent ancestry, whereas comparing a bacteria to an archaea is useless for finding conserved noncoding sequences. CNSs have been detected in vertebrate lineages spanning humans to fish (~400 My divergence), while the most significant CNSs tend to disappear after ~50 My divergence in plants.