How many types of transport RNA are there and what is the difference between messenger RNA and trans

In recent years, the types of tRNA are often involved in popular teaching materials and college entrance examination mock test questions in various places, and it is unanimously believed that there are 61 kinds of tRNA in living organisms. This is based on the fact that there are 61 codons encoding amino acids, and there are 61 anticodons that are paired with the codons on the mRNA, so it is inferred that there are 61 types of tRNAs.

In fact, this is a widely circulated erroneous conclusion.

First, we need to figure out the criteria for determining the type of tRNA. The criteria for classification are different, and of course the conclusions are different.

The first criterion that comes to mind is to divide it according to the kind of amino acids it transports. Since different amino acids are transported by different tRNAs, and each tRNA can only transport 1 amino acid, the types of tRNAs should be the same as the types of amino acids in protein molecules, with a total of 20 species.

The second criterion that comes to mind is to divide it according to the type of anticodon, as mentioned above, the average person thinks that there are 61 anticodons, so it is also considered that there are 61 types of tRNA. But this is not the case: the presence of rare base I (hypoxanthine) on the tRNA and the "L" shaped spatial structure of the tRNA cause the pairing between the third base of the codon and the first base of the anticodon to oscillate.

The first base of the anticodon can be paired with the third base of the codon in many ways, making the tRNA species less than 61 and only about 40.

The third criterion that we should think of, and actually the most reasonable, is to divide according to the structure of the tRNA. In 1965, Hawley et al. determined the order of nucleotides in the primary structure of yeast alanine tRNA, the first nucleic acid. Since then, the determination of RNA primary structure has developed rapidly.

By 1983, there were more than 280 kinds of tRNA with different amino acids and receiving different amino acids!

In summary, no matter which classification we use, there will be no 61 types of tRNA.

61 species. There are 64 kinds of codons, corresponding to 61 kinds of amino acids, and trna, and three of them are stop passwords, which do not correspond to trna

61 species There appear to be 64 codons (three seed codons cannot be expressed).

It must be wrong, one type of transporter RNA can only transport one specific one.

Amino acids, not RNA.

It is true that one transporter RNA can transport only one specific amino acid, but one amino acid can have multiple transporter RNAs.

There are 61 types of high school by default, and this kind of controversial issue is generally not tested.

There are only 61, because there are three that cannot be translated.

1. Form a difference.

Messenger RNA is a class of single-stranded RNA that is transcribed from one strand of DNA as a template and carries genetic information to guide protein synthesis.

Transport RNA, or tRNA for short, is an RNA composed of 76-90 nucleotides, of which 3'The end can be catalyzed by aminoacyl-tRNA synthetase to attach specific kinds of amino acids.

2. The functions are different.

Transport RNA mainly carries amino acids into ribosomes to synthesize proteins under the guidance of mRNA. That is, mRNA is used as a template to translate the sequence of coded nucleotides into the sequence of amino acids in proteins (see Protein Biosynthesis, Ribosomes).

Messenger RNA1, mRNA is a direct template for protein synthesis. Each polypeptide chain has a specific mRNA as a template, so there are many types of mRNA in the cell; It transcribes the genetic information from DNA and carries it to ribosomes, where it controls the order of amino acids in protein molecules in a coded manner as a direct template for protein synthesis.

2. The function of tRNA is to transport amino acids. During protein synthesis, the tRNA forms a complex with amino acids, the monomers required for protein synthesis, to transport amino acids to specific locations in the mRNA in the ribosome.

The function is: it is composed of four arms and four rings, and the paired fragments are called arms, and the unpaired ones are called rings. Ye Bing is an amino acid arm that contains CCA-OH3 on it', this structure is the position where amino acids are accepted.

Opposite the amino acid arm is the anticodon ring. In the middle of it contains an anticodon composed of three phase lead bases, which can be recognized with the codon on the mRNA.

The left ring is the dihydrouracil ring (D-ring), which is involved in the binding of ribosomes. The right ring is a pseudouracil ring (T-C ring), which is associated with the binding of aminoacyl-tRNA synthetase. Between the anticodon and the pseudouracil ring is a variable ring, and its size determines the size of the tRNA molecule.

The transport RNA molecule consists of a short chain of 70 90 nucleotides long and folded into a clover-shaped strand. The two ends of the tRNA strand are close to each other at the ends of the L-shaped structure indicated at the top of the figure. The amino acids are connected at the position indicated by the arrow.

There are 61 kinds of tRNA, corresponding to 61 kinds of codons of amino acids, and among the 64 kinds of codons, 2 are start codons, corresponding to valine and methionine, respectively. 3 are stop codons, which do not correspond to amino acids.

Transfer RNA, also known as transfer RNA, transfer RNA, often referred to simply as TRNA, is an RNA composed of 76-90 nucleotides, the 3 ends of which can be catalyzed by aminoacyl-tRNA synthetase to attach specific kinds of amino acids.

In the process of translation, the tRNA can recognize the codon on the mRNA through its own anticodon, and transport the amino acids corresponding to the codon to the polypeptide chain in ribosome synthesis. Each tRNA molecule can theoretically only be attached to one amino acid, but the genetic code is degeneracy, so that more than one tRNA can be attached to one amino acid.

Three common RNAs

Messenger RNA function: a direct template for protein synthesis.

Transport RNA function: a transport vehicle for ammonia ligand acids.

Ribosomal RNA function: the constituent parts of ribosomes, the site of protein synthesis.

Other small molecule RNA

Intranuclear heterogeneous RNA is the premise of mRNA maturation.

Small RNAs in the nucleus are involved in the splicing and transport of HNRNA.

Nucleolar microRNAs Processing and modification of RRNA.

Cytosolic small RNA proteins are built as components for localizing synthetic signals to recognize body pulses.

Small interfering RNA siRNAs play a central role in the RNA silencing channel and are the guiding elements of the fundamental circle for the degradation of specific messenger RNA (mRNA).

If you are a high school student, please master the first 3 types, and if you are a college student, please understand as much as possible.

a.Clover-shaped structure.

b.Inverted L-shaped structure.

c.Double helix structure.

d.Hairpin wide difference structure.

e.Ultra-blind spiral structure.

Correct answer to the case of caution: a

Transport RNA: A type of RNA consisting of 76-90 nucleotides