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Essay Characteristics of Non-coding RNA

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1.1 Non-coding RNAs The central dogma of molecular biology states that genetic information is conveyed from DNA to mRNA to protein implying that proteins are the main functional genetic output (Crick 1970). Even those few early known non-protein-coding RNAs (ncRNAs) such as transfer RNA, ribosomal RNA, snoRNAs and splicosomal RNAs were in the end required for mRNA processing and translation. The dogma might still be applicable to prokaryotes whose genome consists of approx. 90 % protein-coding genes. In eukaryotes, however, only about 2 % of the genes are protein-coding (Alexander et al. 2010) and those have been studied intensively. The remaining major fraction of the genomic output has for a long time been…show more content…
1.2 Long non-coding RNAs Although the heterogeneous group of long non-coding RNAs (lncRNAs) account with approx. 80 % for the majority of ncRNAs in the mammalian transcriptome (Kapranov 2007), miRNAs have been in the main focus of ncRNA research in the last years. However, there is recent increase in publications describing key functions of lncRNAs in central biological processes (Taft et al. 2010) and diseases.
Trying to categorize non-coding transcripts, lncRNAs have been defined as > 200 nt long sequences with low or no protein-coding potential. They are weakly conserved between species and undergo (in most cases) 5- capping, canonical polyadenylation and splicing just like mRNAs. LncRNAs can also be grouped by their genomic proximity to neighboring coding transcripts (Johnsson et al. 2014):
- Sense
- Antisense, when overlapping with exons of another transcript on the same or opposite strand
- Intronic, when derived from an intron of another transcript
- Bidirectional, when its expression and a neighboring coding transcript on the opposite strand is initiated in close genomic proximity
- Intergenetic, when transcripted from a sequence between
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