Protein synthesis
It stores information for protein synthesis, DNA executes instructions RNA is encoded in DNA, but the biological activity of most, is performed by proteins. Exact synthesis of protein is important as this for organisms and cells to function properly. The linear sequence of amino acids in the protein of each, we saw in Chapter 3 to determine the activity and the three-dimensional structure. Thus, the assembly of amino acids is very important for the production of functional protein to its correct position, as encoded by DNA.
Base code “keyword” of three, defining each carry a copy of genetic information in the form of the DNA sequence of the amino acid specific RNA (mRNA is). It is the key to decipher the code word of transfer RNA mRNA (tRNA is). If the next codeword of mRNA is required, then bonded to the terminal of the growing peptide chain, any type of amino acid has the mRNA species that result. Attached to the amino acid since it contains the nucleotide sequence of the three possible base pair with the complementary code words of the mRNA in a suitable mRNA, mRNA molecule each particular is chosen at each step.
Associated with a set of proteins for the formation of ribosomal ribosomal RNA (the rRNA). Complex structures of these moves physically mRNA molecules catalyze the assembly of amino acids in the protein chain. I also bind to other molecules accessories necessary for protein synthesis and mRNA. Each of these include molecules or ribosomal RNA molecules unique ribozyme is composed of large and small subunits.
Translation is the whole process that uses the nucleotide sequence of the sequence of mRNA, joining the amino acids in proteins. In the cells of all three types of RNA, is involved in the basic protein synthesis, in fact, the development of functional three different RNA is a key molecule in the origin of life probably. The RNA of each, perform the tasks of that particular has been described in this section, protein and how events biochemical in the synthesis of elements required protein, are described in the last section of the chapter .
Deoxyribonucleotide of DNA adenine, cytidine, guanine, and contained the uracil include adenine, cytidine, guanine, thymine nucleotide since, is 4 inches,,, nucleotides of the RNA linear 4 protein only taken separately groups may nucleotides are needed to represent each amino acid may be a 20 amino possibilities coding arrangement. Code to be used (ie, amino acids), must be able to describe the words of at least 20.
The (42) or 16, if they are used for encoding one amino acid, dibasic-only can different code words would be enough to form it. If you are used for each codeword, any group of three nucleotides may be formed (or 43) 64 of the next codeword. Each code by a group of nucleotides of three or more, have more than enough units to encode the 20 amino acids. It is mathematically possible many of the coding system thereof. However, from the starting point of the mRNA in a triplet code in three nucleotides of all, the actual use of the genetic code of the cell, are “read”. Respectively, it is called triplet codon. Of the 64 possible codons, specify different amino acids 61, the three stop codons in the genetic code. Table 4-2 shows the amino acid most of the are encoded by more than one codon. Tryptophan and methionine – just one – 2 is the other extreme, leucine arginine, and serine, have each, one codon that are defined by different codons of six. Various codons for a given amino acid, which is said it is a synonym. Itself, called the mean degenerate code that includes redundancy.
Ynthesis chain of all proteins of eukaryotic cells and prokaryotic starting from the amino acid methionine. August and the amino-terminal methionine CUG and the initiator codon is used as a methionine initiation codon at Occasionally eukaryotes, initiation of mRNA Most specifying the mRNA of several bacteria (start) codon, is used GUG You. UAG three codon UAA, and UGA, the carboxyl terminus of the intracellular protein chain of almost all of the brand does not represent the (Terminator) stop signal by specifying the amino acid. To stop codon, the sequence of execution codon, is called reading frame from the start of a particular site. Sequences of the component ribonucleotides in groups of three to accurate linear sequencing mRNA of amino acids of the correct linear proteins such synthesis and protein chains is started, and outputs a signal to stop.
Because the genetic code commaless duplicate triplet code is determined theoretically from the mRNA can be converted to the leading three frames. In practice, mRNA several are shown to include redundant information that can be converted to produce different polypeptides, the reading frame to another. Before functional protein is produced, the stop codon present in the possible reading frames in the other two, and exit the translation, the majority of the mRNA, however, only can be read in one frame. Unusual coding sequence Another happen to cause the frame shift. In this case, read the four nucleotides as amino acids, you can continue reading triplets, back up the database and then, in the new framework, machinery of protein synthesis, triplet of all subsequent chain termination occurs You can be you can read. The frameshift these were not a common event, but such cases tens are known.