Balakirev Evgeniy S, Ayala Francisco J
Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92697-2525, USA.
Annu Rev Genet. 2003;37:123-51. doi: 10.1146/annurev.genet.37.040103.103949.
Pseudogenes have been defined as nonfunctional sequences of genomic DNA originally derived from functional genes. It is therefore assumed that all pseudogene mutations are selectively neutral and have equal probability to become fixed in the population. Rather, pseudogenes that have been suitably investigated often exhibit functional roles, such as gene expression, gene regulation, generation of genetic (antibody, antigenic, and other) diversity. Pseudogenes are involved in gene conversion or recombination with functional genes. Pseudogenes exhibit evolutionary conservation of gene sequence, reduced nucleotide variability, excess synonymous over nonsynonymous nucleotide polymorphism, and other features that are expected in genes or DNA sequences that have functional roles. We first review the Drosophila literature and then extend the discussion to the various functional features identified in the pseudogenes of other organisms. A pseudogene that has arisen by duplication or retroposition may, at first, not be subject to natural selection if the source gene remains functional. Mutant alleles that incorporate new functions may, nevertheless, be favored by natural selection and will have enhanced probability of becoming fixed in the population. We agree with the proposal that pseudogenes be considered as potogenes, i.e., DNA sequences with a potentiality for becoming new genes.
假基因被定义为基因组DNA的非功能性序列，最初源自功能基因。因此，人们认为所有假基因突变都是选择性中性的，并且在群体中固定下来的概率相等。然而，经过适当研究的假基因通常表现出功能作用，如基因表达、基因调控、遗传（抗体、抗原及其他）多样性的产生。假基因参与与功能基因的基因转换或重组。假基因表现出基因序列的进化保守性、核苷酸变异性降低、同义核苷酸多态性相对于非同义核苷酸多态性过剩，以及其他在具有功能作用的基因或DNA序列中预期会出现的特征。我们首先回顾果蝇相关文献，然后将讨论扩展到在其他生物体假基因中鉴定出的各种功能特征。通过复制或反转录产生初始可能不受自然选择作用，前提是源基因仍具有功能。然而，纳入新功能的突变等位基因可能会受到自然选择的青睐，并在群体中固定下来的概率会增加。我们赞同将假基因视为原基因的提议，即具有成为新基因潜力的DNA序列。
