In evolutionary biology, an orphan gene is a gene that has limited phylogenetic distribution. This also means that these genes lack detectable homology to organisms outside such phylogenetic distribution. In many cases homology is determined by sequence similarity, shared domains or synteny.
The two possible modes for the generation of orphan genes are duplication followed by quick divergence, and de novo evolution from non-coding DNA.
In bacterial literature, orphan genes are also referred to as ORFans, a play on open reading frame.
Read more about Orphan Gene: Definitions, Properties, Significance in Evolutionary Biology
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“For the LORD your God is God of gods and Lord of lords, the great God, mighty and awesome, who is not partial and takes no bribe, who executes justice for the orphan and the widow, and who loves the strangers, providing them food and clothing.”
—Bible: Hebrew, Deuteronomy 10:17,18.