Theory suggests three alternative   outcomes in the evolution of duplicate genes: (i) one copy may simply become   silenced by degenerative mutations (nonfunctionalization); (ii) one copy may   acquire a novel, beneficial function and become preserved by natural   selection, with the other copy retaining the original function   (neofunctionalization); or (iii) both copies may become partially compromised   by mutation accumulation to the point at which their total capacity is   reduced to the level of the single-copy ancestral gene (subfunctionalization)   (1–12). Because the vast majority of mutations affecting fitness are   deleterious (13), and because gene duplicates are generally assumed to be functionally   redundant at the time of origin, virtually all models predict that the usual   fate of a duplicate-gene pair is the nonfunctionalization of one copy. The   expected time that elapses before a gene is silenced is thought to be   relatively short, on the order of the reciprocal of the null mutation rate   per locus (a few million years or less), except in populations with enormous effective   sizes (11, 12).

理论表明，在重复基因的进化过程中，有三种不同的结果：（i）一个拷贝可能被退化的突变（非功能化）所沉默；（ii）一个拷贝可能获得一种新的、有益的功能（新功能化），并被自然选择所保留，而另一个拷贝则保留了原来的功能；或（iii）两个拷贝可能因突变累积而部分表达，直至其总容量降低到单拷贝祖先基因的水平（子功能化）（1-12）。因为影响适应能力的绝大多数突变是有害的（13），并且由于基因重复在起源时通常被认为是功能上的冗余，几乎所有的模型都预测一个重复基因对的通常命运是一个拷贝的非功能化。除了具有巨大个体数的群体（11，12），考虑每个基因座的不同无义突变率级别（几百万年或更少），基因沉默前的预期时间被认为是相对较短的。