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Why can some genes remain without an assigned function after genome annotation?

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Computer-generated model of anthrax toxin showing seven differently colored protein units, with a small gold molecule representing a drug bound to the protein structure. — bioinformatics This computerized image of anthrax shows the various structural relationships of seven units within the protein and demonstrates the interaction of a drug (shown in yellow) bound to the protein to block the so-called lethal factor unit. Bioinformatics plays an important role in enabling scientists to predict where a drug molecule will bind within a protein, given the individual structures of the molecules.

During genome annotation, scientists use bioinformatics to identify candidate genes, often called open reading frames (ORFs), by scanning DNA sequences for specific features like start and stop codons.12

Once these candidates are identified, researchers typically attempt to assign functions by comparing the sequences to known genes in other organisms, relying on the evolutionary conservation of gene sequence and function. However, some genes remain unassigned after this process because their sequences do not sufficiently resemble those of previously characterized genes, making it impossible to deduce their roles through simple comparison. These genes remain without an assigned function until further research, such as functional genomics experiments, can reveal their specific biological roles.21