Pseudogenes
No longer function but are still carried along with functional DNA, provide evidence of a common ancestor
Pseudogenes are DNA sequences that closely resemble functional genes but have lost their ability to code for proteins due to mutations. Pseudogenes were once thought to be “junk DNA” with no biological function. However, recent studies have suggested that pseudogenes can have different functions, some of which are still not fully understood. There are three types of pseudogenes: processed, duplicated, and unitary.
Processed pseudogenes are formed from reverse transcription of mRNA and subsequent integration into the genome, and lack introns and regulatory elements. Duplicated pseudogenes arise from gene duplication events, after which one of the copies becomes inactivated by accumulating mutations. Unitary pseudogenes correspond to genes that were once functional, but underwent inactivation by mutations while retaining introns and regulatory elements.
Although most pseudogenes do not produce functional proteins, some are transcribed into non-coding RNAs (ncRNA) that can play important roles in gene regulation. For example, some pseudogene-derived ncRNAs have been shown to regulate the expression of related genes in cis or trans by modulating chromatin structure, transcriptional activity, mRNA splicing, and translation. Pseudogene-derived ncRNAs may also serve as decoys for microRNAs, or interact with proteins or other RNAs to control cellular processes and signaling pathways.
In summary, pseudogenes may have more diverse functions than previously thought, and their study may unveil new aspects of gene regulation and evolution.
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