Is Codon DNA Or RNA: 7 Facts You Should Know!

The term codon is used to refer to an mRNA triplet. A triplet is the term used to describe a group of three nucleotide bases on DNA. Let us talk about these two.

The three nucleotides make up a “codon“, which designates one amino acid in the polypeptide chain. On the other hand, a single amino acid is determined by the “triplet code”, which consists of three nucleotides.

Below we are going to discuss some important facts about triplets and codons in detail. We will also learn about the term “genetic code”, formation of codons, some examples of codons, how to read or identify them and so on.

What is genetic coding?

The genetic code is defined as the connection between the DNA bases sequence that is A, C, G and T present in a gene and the matching protein sequence encoding it. Let us discuss.

Genetic code is the combination of rules that the living cells uses to convey information that encoded inside the genetic materials like DNA, RNA sequences of nucleotide triplets or codons in the proteins. All species share a great deal of genetic similarity, which is stated in a table of 64 items.

After the gene is synchronized inside the RNA, the four RNA bases are found to represent the triplets, that is, thymine gets replaced by the uracil. The molecules of DNA and RNA are the two languages that are written in the form of nucleotides. Codons play an important role by which these two languages can be translated into one another.

How are codons formed?

A codon is referred to the sequence of 3 nucleotide bases present in DNA and RNA strands which is the component of genetic code. Let us discuss how codons are formed. 

Codons are closely similar to the single amino acids. The following ways show the formation of codons:

  • The formation of codons or the system of genetic coding are due to the different alignment of the 4 bases inside the DNA or RNA.
  • According to this system, a codon consists of 3 bases or letters.
  • A total of 64 different combinations of DNA or RNA codons exists.
  • A triplet codon is formed by a combination of three nucleotides with four nitrogenous bases that encodes with only one amino acid.
  • Therefore, the possible number of amino acids formed is 4 x 4 x 4 = 64, whereas naturally there are only 20 amino acids that exist.
DNA and RNA codons- Image Credit: Wikipedia

Can codons have both DNA and RNA?

A codon is defined as the sequence of DNA or RNA having trinucleotide that connects with a particular amino acid. Let us discuss if codons can have both DNA and RNA.

Every codon is a set of three bases or letters that consist of both DNA and RNA in them. They altogether form the instructions for DNA or RNA. As DNA and RNA consist of only four nucleotides in them, thus there will be possibly 64 codons.

DNA and RNA codon tables- Image Credit: Wikipedia

Out of 64 codons, 61 codes are for amino acids, that represent the building blocks of protein. DNA contains four nucleotide bases namely- adenine (A), guanine (G), cytosine (C) and thymine (T). Whereas RNA consists of the nucleotides such as adenine, guanine, cytosine and uracil (U).

Codon example

Out of total number of 64 codons, there are 61 codons that represent amino acids, and the other three are represented as the stop signals. Let us see some examples of codons.

Regardless of any sort of organism, the codes are the same for every creature. Sometimes due to the possibility of more than one codon encoding the same amino acid, the genetic code is said to as faulty or redundant, for instance:

  • CGU would code for arginine in animals as well as in bacteria, but exceptions exist.
  • CGU denotes arginine in case of animals and also for bacteria, but sometimes exceptions may exist.
  • The codon AUG codes or denotes methionine which acts as the initiator codon or the start codon of a protein. It is present at the emergence of every mRNA.
  • The amino acid named glutamine is denoted by the codon CAG.
  • TAA is denoted as the stop codon.

How to read DNA codons?

Codons having three bases or letters found in genetic code can be sequenced in three different ways. These ways are known as Reading Frames. Let us learn how to read them.

According to the genetic code, with the help of reading frames all the genes and the DNA sequences can be read in three (because there are three letters) various ways. These bases or letters are- first letter, second letter and third letter:

  • Due to different properties of amino acids, every single frame will form a specific sequence of various amino acid.
  • If we take an example of the gene CGAGCCTCC, in the first frame or position, it consists of the codons- CGA, GCC, TCC.
  • If the reading is taken from the second frame or position, then it consists of codons- GAG and CCT.
  • Now, for the third frame or position, it comprises of codons- AGC and CTC.
  • For the second and third reading frames, they only include two full codons since the code is processed as triplets’ codons for every frame.
  • Out of the total frames that could be read, there is actually only one correct frame that produces the sequence of protein. The other two frames being the wrong ones.
  • Normally in the cells, the actual or the correct frame in which the sequence of protein is translated is denoted by the Start codons and end with the Stop codons.
The three letters or bases (first, second and third) of codon table sequencing 20 amino acids- Image Credit: Wikipedia

How to code DNA to mRNA?

The translation process occurs when the instructions of decoding in order to produce proteins take place. Let us discuss how DNA are coded to mRNA.

Expression of a gene refers to the production of protein corresponding it. This is a two-step process that include- transcription and translation. The process is carried out by these two important steps:

  • In the initial step, the instruction in DNA is conveyed to the molecule of messenger RNA (mRNA) through the process known as transcription.
  • While transcription takes place, the DNA in a gene act as a template for complementary base-pairing.
  • RNA polymerase II is a kind of enzyme that helps in catalyzing the molecule of pre-RNA which gets converted into the mature mRNA.
  • The mRNA formed is the duplicate of the gene which is single stranded. This is to be then translated into the molecule of protein.
  • In the second important step of gene expression, that is, during the process of translation, the mRNA is “read” as stated by the genetic code, that combines or links the sequence of DNA to the sequence of amino acid chains in the proteins.
  • Of the total codons of 64, there are only 3 codons that do not take part in coding for any amino acids and therefore ends the procedure of translation.
Genetic code (transcription and translation)- Image Credit: Wikipedia

What are codons attached to?

A single codon stands for an amino acid whereas the codon sequence gives the information about the amino acids present in protein. Let us see what codons are bonded to.

Every codon is generally attached to a particular amino acid. Some particular amino acids are coded for by the triplet codons. In general, for the 20 amino acids present in nature there are 64 triplets’ codons to code them.

A series of codons in part of a messenger RNA (mRNA) molecule corresponding to a single amino acid- Image Credit: Wikipedia

The protein that should be produced is result of the specific sequence of amino acids. During the process of translation, the amino acids altogether get combined to produce a total number of proteins.

Conclusion

Individually codon codes only single amino acid, numerous amino acids are roundabout multiple of codons because there are 64 thinkable groupings of bases of DNA.

Scroll to Top