MRNAs in the context of Post-transcriptional modification

MRNAs in the context of Post-transcriptional modification

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⭐ Core Definition: MRNAs

Messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein.

mRNA is created during the process of transcription, where an enzyme (RNA polymerase) converts the gene into primary transcript mRNA (also known as pre-mRNA). This pre-mRNA usually still contains introns, regions that will not go on to code for the final amino acid sequence. These are removed in the process of RNA splicing, leaving only exons, regions that will encode the protein. This exon sequence constitutes mature mRNA. Mature mRNA is then read by the ribosome, and the ribosome creates the protein utilizing amino acids carried by transfer RNA (tRNA). This process is known as translation. All of these processes form part of the central dogma of molecular biology, which describes the flow of genetic information in a biological system.

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MRNAs in the context of Xist

Xist (X-inactive specific transcript) is a non-coding RNA transcribed from the X chromosome of the placental mammals that acts as a major effector of the X-inactivation process. It is a component of the Xic – X-chromosome inactivation centre – along with two other RNA genes (Jpx and Ftx) and two protein genes (Tsx and Cnbp2).

The Xist RNA, a large (17 kb in humans) transcript, is expressed on the inactive chromosome and not on the active one. It is processed in a similar way to mRNAs, through splicing and polyadenylation. However, it remains untranslated. It has been suggested that this RNA gene evolved at least partly from a protein-coding gene that became a pseudogene. The inactive X chromosome is coated with this transcript, which is essential for the inactivation. X chromosomes lacking Xist will not be inactivated, while duplication of the Xist gene on another chromosome causes inactivation of that chromosome.

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LINKED FROM (PARENTS)
← Xist
LINKS TO (CHILDREN)
Eukaryote → RNA → Transcription (genetics) → Cell nucleus → Post-transcriptional modification → Cytoplasm → Translation (genetics) → Ribosome → Molecule → Genetic sequence → Gene → Protein biosynthesis → Protein → Transcription (biology) → Enzyme → RNA polymerase → Primary transcript → Pre-mRNA → Introns → Amino acid sequence → RNA splicing → Exons → Mature mRNA → Amino acids → Transfer RNA → Translation (biology) → Central dogma of molecular biology →