Translation is the final step in the realization of genetic information. Transfer RNA (tRNA) translates strands of messenger RNA (mRNA) into protein sequences in this process. Errors in this translation are also called mutations.
What is translation?
Translation is the process of converting the genetic code into chains of proteins. During translation, the mRNA is read. The reading results in the synthesis of proteins. During translation, the genetic code is converted into chains of proteins. The substep before translation is also known as transcription. During this transcription, a single-stranded DNA transcript is created. This transcript corresponds to a DNA subsection, each belonging to one gene. The transcription is carried out by the enzyme RNA polymerase. The end product of the transcription is the so-called mRNA. During the subsequent translation, this mRNA is read. The reading results in the synthesis of proteins. At the end of translation, the mRNA has thus been translated into protein chains. Translation takes place in the ribosome of a cell, i.e. in the cell organelle. It is the final realization step for genetic information. In this process, mRNA emerges from the nucleus into the cytoplasm and threads itself into ribosomes.
Function and task
Translation serves to translate an mRNA sequence into a protein sequence. Each mRNA strand consists of a chain of bases. The bases are present in triplets, that is, three consecutive parts each. Each base triplet of the mRNA codes for a specific amino acid and is also called a codon. In mRNA there are start codons, norm codons and stop codons. The start codon consists of the bases adenine, guanine and uracil. There are three different stop codons, which are abbreviated as UGA, UAG and UAA. Accordingly, they also consist of uracil, guanine and adenine, but in a different order. A translation always starts at the start codon and always ends at a stop codon. The norm codons are all the rest of the base triplets. They each code for a specific amino acid. The start codon AUG codes for methionine. The three stop codons are exclusively intended to terminate translation and accordingly do not code for amino acids. In the next step of translation, important tasks are assigned to the transfer RNA. This tRNA is short RNA that transports the correct amino acids to the corresponding codon on the mRNA. tRNA molecules are loaded with amino acids, enzymes and proteins. They help the ribosome translate the mRNA into protein sequences. The construction of protein sequences takes place with the help of their smallest components, i.e. amino acids. When the tRNA has transported the mRNA to a specific ribosome, it binds the amino acids to other amino acids and forms peptide chains in this way. tRNA always has several arms. An amino acid binds to one of the arms at a time. Opposite to it is its complementary anticodon, each of which belongs to the mRNA base codon. In methionine, for example, the tRNA has the anticodon UAC. This anticodon does not match every base triplet, but only to the AUG codon. In this way, the base sequence AUG codes in the mRNA for the amino acid methionine. Each of the amino acids depends on a specific tRNA. Otherwise, it cannot be transferred to the corresponding codon of the mRNA. Which tRNA is responsible for which amino acid is determined by its anticodon. In the ribosome, a first tRNA attaches to the mRNA at the start codon. Next to this first tRNA, a second one with a specific amino acid is added. The linkage of the now adjacent amino acids is realized by a peptide bond. The first tRNA leaves its amino acid at the arm end of the second and leaves the ribosome. There are now two amino acids on the second tRNA. When the first tRNA has left the ribosome again, a third tRNA with its special amino acid attaches to the mRNA. The process continues in this way as long as no base triplet with a stop codon appears. As soon as a stop codon appears, the peptide chain detaches. The process cannot continue because there is no associated tRNA for stop codons.
Diseases and disorders
With the incorrect realization of genetic information, diseases can arise. Mutations thus sometimes present themselves during translation. Point mutations are spontaneous or induced changes in the genetic material that affect only one nucleic base.Some point mutations remain inconsequential. This is the case when an amino acid can be encoded by several codons. This may result in identical proteins. If, on the other hand, one base of the mRNA is replaced with another, point mutations are also referred to as substitutions. This results in the insertion of a different amino acid in a coding region. In this way, an altered protein is formed, which may no longer be able to perform its function. Sickle cell anemia is an example of such a mutation during translation. This phenomenon is a hereditary disease of red blood cells. Chronic anemia sets in. As a result, organ damage occurs due to oxygen deficiency. However, an mRNA strand can also be shifted during translation. If the reading frame is shifted, the strand loses its actual meaning and original function. Deletions often occur in this context. This means that bases are lost. Possibly also an insertion occurs and bases are added. Deletions and insertions are usually more severe than substitutions and can result in severe malformations or physical dysfunction.
