Nei and his students studied the evolutionary patterns of a large number of multigene families and showed that they generally evolve following the model of a birth–death process. In some gene families, this process is very fast, caused by random events of gene duplication and gene deletion and generates genomic drift of gene copy number.
Nei and his students investigated the evolutionary patterns of numerous multigene families, demonstrating that they generally follow a birth-death process model. In some gene families, this process is rapid due to random events like gene duplication or deletion, leading to changes in the number of copies of those genes.