Two or more genes are homolog if thay have similar sequences. homolog sequences between species are called orthologs (caused by speciation events) and homolog sequences in an species are called paralogs (caused by duplication events).

I would like to know what is expression pattern of paralogs or orthologs in an specific tissue. Are paralog (or ortholog) genes have same expression in a tissue or they express different?

I hope my question is clear, but if it has mistakes I appreciate your corrections.


The evolution of new genes is frequently associated with gene duplication. The paralogous genes are then free to evolve on their own into new functions over time. Sometimes (usually) the paralog will end up with a frame shift, or stop codon that inactivates it. But your question is lacking the element of time. At the instant of gene duplication, each copy is identical. However, one copy may lack the control elements (usually upstream), and not be transcribed. Or one copy may eventually evolve a new, tissue specific function. But whether the copy is inactivated, or evolves a new function, or remains active is not the same for every instance. It depends on how each copy changes under the influences of mutation and selection.

  • $\begingroup$ Nice answer. can you please introduce me some articles talking about this topic? $\endgroup$ – MySky Nov 20 '17 at 13:25
  • $\begingroup$ I just Googled: "gene duplication" paralog function. and got a lot of informative hits. $\endgroup$ – Karl Kjer Nov 20 '17 at 15:40

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