A pseudogene is a nonfunctional version of a gene. It is a gene that has lost its ability to produce a functional protein due to mutations or other changes in its DNA sequence. Pseudogenes can arise through various mechanisms, such as gene duplication, retrotransposition, and gene conversion. Unlike subfunctional paralogs, which are copies of a gene that have diverged in function but still retain some level of activity, pseudogenes do not contribute to the production of functional proteins. Mads-box gene and homeobox gene are examples of functional genes, while a pseudogene is a nonfunctional version of a gene.