Central Dogma (Gene Expression): Definition, Steps, Regulation. The central dogma of molecular biology explains that the information flow for genes is from the DNA genetic code to an intermediate RNA copy and then to the proteins synthesized from the code.

How genes in DNA can provide instructions for proteins. The central dogma of molecular biology: DNA → RNA → protein.

The central dogma states that the pattern of information that occurs most frequently in our cells is:

• From existing DNA to make new DNA (DNA replication?)
• From DNA to make new RNA (transcription)
• From RNA to make new proteins (translation).

Translation of an mRNA molecule by the ribosome occurs in three stages: initiation, elongation, and termination.

An anticodon is a trinucleotide sequence complementary to that of a corresponding codon in a messenger RNA (mRNA) sequence. An anticodon is found at one end of a transfer RNA (tRNA) molecule.

Translation begins when an initiator tRNA anticodon recognizes a codon on mRNA. The large ribosomal subunit joins the small subunit, and a second tRNA is recruited. As the mRNA moves relative to the ribosome, the polypeptide chain is formed.

Each three-letter sequence of mRNA nucleotides corresponds to a specific amino acid, or to a stop codon. UGA, UAA, and UAG are stop codons.

There are 3 STOP codons in the genetic code – UAG, UAA, and UGA. These codons signal the end of the polypeptide chain during translation. These codons are also known as nonsense codons or termination codons as they do not code for an amino acid.

Without stop codons, an organism is unable to produce specific proteins. The new polypeptide (protein) chain will just grow and grow until the cell bursts or there are no more available amino acids to add to it.

In the standard bacterial codon table, there are three stop codons, TAG, TGA, and TAA (UAG, UGA, and UAA on mRNA), which are recognized by two class I release factors, RF13 and RF2. In the few coding sequences available at that time, TAA was observed to be the most abundant stop codon.

Most codons in messenger RNA correspond to the addition of an amino acid to a growing polypeptide chain, which may ultimately become a protein; stop codons signal the termination of this process by binding release factors, which cause the ribosomal subunits to disassociate, releasing the amino acid chain.

The 42mer mRNA analogs containing the canonical stop (UGA, UAA, UAG) or sense (UAC, UGG) codons are indicated.

Three sequences, UAG, UGA, and UAA, known as stop codons, do not code for an amino acid but instead signal the release of the nascent polypeptide from the ribosome….Inverse RNA codon table.

The other major identity element in tRNATrp is the CCA anticodon,39 which is conserved in tRNAOther but does not appear to be a major element for recognition by LysRS1:LysRS2, compatible with the lack of aminoacylation by TrpRS.

The codon for Methionine; the translation initiation codon. Usually, protein translation can only start at a Methionine codon (although this codon may be found elsewhere within the protein sequence as well). In eukaryotic DNA, the sequence is ATG; in RNA it is AUG.

Codon-Amino Acid Abbreviations

In this table, the twenty amino acids found in proteins are listed, along with the single-letter code used to represent these amino acids in protein data bases….Codon list.

The amino acid arginine has 6 mRNA codons : CGU, CGC, CGA, CGG, AGA and AGG.

Redundancy in the genetic code means that most amino acids are specified by more than one mRNA codon. For example, the amino acid phenylalanine (Phe) is specified by the codons UUU and UUC, and the amino acid leucine (Leu) is specified by the codons CUU, CUC, CUA, and CUG.

Codons are three letter genetic words: and the language of genes use 4 letters (=nitrogenous bases). Hence 64 words are there in genetic dictionary, to represent 20 amino acids that the biological organisms use.

…by a unique sequence, or codon, of three of the four possible base pairs in the DNA (A–T, T–A, G–C, and C–G, the individual letters referring to the four nitrogenous bases adenine, thymine, guanine, and cytosine).

A codon is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or stop signal during protein synthesis. Codons provide the key that allows these two languages to be translated into each other. …

A codon is a trinucleotide sequence of DNA or RNA that corresponds to a specific amino acid. The cell reads the sequence of the gene in groups of three bases. There are 64 different codons: 61 specify amino acids while the remaining three are used as stop signals.