Dubbed as neofunctionalization, one of the two duplicated genes can be released from functional constraint and acquire new functions, whereas the other gene performs the original functions (Innan and Kondrashov 2010).
Both copies must be maintained in order to perform the original function of the gene [ 21, 22].
The case of TFIIAγ genes agree with previous notion that subfunctionalization would lead to functional specialization when one of the duplicate genes became better at performing the original function of the progenitor gene [ 22].
The subfunctionalization model suggests that neutral mutations in duplicate genes weaken or alter the original function so that both copies are maintained to perform the original function [ 35, 36].
Paralogs can be retained when both copies continue to perform the original function due to dosage benefit, i.e., by gene conservation [ 1, 6, 8], also described as "more of the same" mechanism [ 5].
Expression studies will need to be performed to determine if the original function has been partitioned among the four duplicates (subfunctionalization) or if Dappu_InR4 has acquired new function by neofunctionalization.
Was the order to do with the original function of the objects, or was it sculptural?
This duplication has exactly the same freeing effect as does gene duplication, in which the duplication allows one of the genes to evolve, presumably in many cases through intermediate forms involving loss of function, to code for new proteins because the other member of the pair continues to perform the original gene's function.
It is thus possible that the members of the PGRS and MPTR subfamilies have evolved to function as a source of antigenic variation; a function which probably differs from the original function still performed by the members of the "ancestral-type" subgroup (including the members present within and associated with the ESAT-6 (esx) gene cluster regions).
Two organs (or genes) perform the same function and then one becomes more specialized for the original function while the other takes on a different role.
