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Other functional regions of the non-coding DNA fraction include regulatory sequences that control gene expression; scaffold attachment regions; origins of DNA replication; centromeres; and telomeres. Some non-coding regions appear to be mostly nonfunctional, such as introns, pseudogenes, intergenic DNA, and fragments of transposons and viruses.
The regulatory functions commonly associated with conserved non-coding regions are thought to play a role in the evolution of eukaryotic complexity. On average, plants contain fewer CNSs per gene than mammals. This is thought to be related to their having undergone more polyploidization, or genome duplication events.
The mtDNA control region is an area of the mitochondrial genome which is non-coding DNA. This region controls RNA and DNA synthesis. [1] It is the most polymorphic region of the human mtDNA genome, [2] with polymorphism concentrated in hypervariable regions. The average nucleotide diversity in these regions is 1.7%. [3]
However, it is now known that the untranslated region of mRNA is involved in many regulatory aspects of gene expression in eukaryotic organisms. The importance of these non-coding regions is supported by evolutionary reasoning, as natural selection would have otherwise eliminated this unusable RNA.
Cis-regulatory elements (CREs) or cis-regulatory modules (CRMs) are regions of non-coding DNA which regulate the transcription of neighboring genes.CREs are vital components of genetic regulatory networks, which in turn control morphogenesis, the development of anatomy, and other aspects of embryonic development, studied in evolutionary developmental biology.
The roles of non-coding RNAs: Ribonucleoproteins are shown in red, non-coding RNAs in blue. A non-coding RNA (ncRNA) is a functional RNA molecule that is not translated into a protein. The DNA sequence from which a functional non-coding RNA is transcribed is often called an RNA gene.
Gene prediction is one of the key steps in genome annotation, following sequence assembly, the filtering of non-coding regions and repeat masking. [3] Gene prediction is closely related to the so-called 'target search problem' investigating how DNA-binding proteins (transcription factors) locate specific binding sites within the genome.
Additionally, non-protein coding regions such as genes for ribosomal RNA and transfer RNA, regulatory sequences, origins of replication, centromeres, telomeres, and scaffold attachment regions are considered as functional elements. (See Non-coding DNA for more information.)