Transcription and Translation



Transcription of RNA from DNA

One of the central concepts of biology is that RNA is transcribed from DNA in a process called transcription. There are several types of RNA that can be transcribed including mRNA, rRNA and tRNA. mRNA (messenger RNA) is the type of RNA which codes for a protein and is ultimatley used to translate protein on the ribosome.





Several post-transcriptional processing steps occur in eukaryotes after the initial transcription of pre-mRNA. The intial pre-mRNA has introns spliced out and exons spliced together. Also, a 5' G-cap is added to the 5' (5 prime) end, and a 3' poly-A tail (many adenines- about 200) are added to the 3' (3 prime) end.

Translation of Protein from RNA

Protein is translated from mRNA on a structure called the ribosome. Ribosomes consist of many subunits of protein and rRNA.



RNA is transcribed from DNA by an enzyme called RNA Polymerase in a process called transcription. Protein is then translated from RNA (mRNA) on the ribosome in a process called translation. Thus, the flow of information in a cell is from DNA to RNA to protein which is referred to as the central dogma of molecular biology.



Three types of RNA are involved in the translation of protein at the ribosome. mRNA (messenger RNA) carries the code for the sequence of amino acids to build, tRNA (transfer RNA) serves as the adaptor which recognizes each codon on the mRNA and carries the corresponding amino acid to the ribosome. rRNA (ribosomal RNA) is a constituent of the ribosome itself and carries out critical enzymatic functions.

A diagram showing the role of 3 types of RNA in translation of protein