Question

which of the following is the best argument that a hypothetical gene is "real" (actually encodes a functional product)?

1) The gene encodes a long (3000 bp) open reading frame
2) You were able to recover a clone from a cDNA library using the sequence of your gene as a probe.
3) There is homologous sequence found in a closely related species.

Answer 1

3) There is a homologous sequence found in a closely related species.

This is one of the ways by which we can identify if the hypothetical gene encodes for a functional product. The homologous genes are also referred to as conserved hypothetical genes and due to their identification are another species; it is likely that it produces an important product that is functional. In the first argument by simply having a 3000bp ORF does not necessarily make it a functional product. The cDNA can be also extracted from any sequence and it does not necessarily has to be a functional product encoding gene