Important Topic of Biology: Genetic Code

Genetics contains information about the various characters and characteristics of living creatures. Genetic information is passed on from generation to generation by code. It determines the characteristics of an organism, for example, whether it is a bacterium or a person. The genetic code that a person has controls the entire process of life.

We will learn about the definition of genetic code and its structures in this section.

What is the meaning of genetic code?

We can define genetic code as a set of rules for living cells to translate information entered into genes (DNA or mRNA sequences). Ribosomes are responsible for completing the translation process. They use tRNA molecules (transfer RNA) to transport amino acids and read mRNA, three nucleotides at a time, to link amino acids to a specified system (messenger RNA).

Also Check: 

• Genetic Code Codons Amino Acids
• Mutation and Genetic Code
• Nuclei Acids RNA and DNA

Genetic code features

It is interesting to look at the intricate process of genetic engineering and to copy it into offspring to create a new set of genes. Millions of chemical reactions occur in the cell and require a well-regulated environment to perform all the biochemical processes.

Let us now continue to better understand the key features of the genetic code.

Each codon has three bases, resulting in a total of 64 codons. Only 61 out of 64 codons can produce amino acids. The remaining three are used as stopping codons during the translation process.

One codon is responsible for directing the reaction leading to the production of amino acids. As a result, the process is special.

The synthesis of other amino acids may require many codons. This is called genetic code degeneracy. For example, Valine (Val) integration requires four consecutive codons – GUA, GUC, GUU, and GUG.

Codons play a role in the production of mRNA; on the other hand, mRNA is responsible for protein production.

Genetic code is also unique because it is found all over the world. It means that a single codon results in the production of single amino acid. Phenylalanine (Phe), for example, has the genetic code UUU. All living things are shared.

This indicates that the Phe of the bacterium will be compared to that of a human.

Codons can have multiple functions sometimes. AUG, for example, is the genetic code of Methionine (Met). It also acts as the first codon or launcher.

The basic genetic code is most commonly found in all living things.

Genetic Code: Properties and Key Features

The genetic code is a vital aspect of biology, playing a key role in protein synthesis. Below are the structured properties and features of the genetic code:

1. Triple Code

• The genetic code is represented by codons, which are sequences of three consecutive nucleotides in mRNA (5′ → 3′).
• Codons specify amino acids, making the genetic code a triplet code.
• There are 64 codons, derived from four nucleotide bases (A, G, C, U). Out of these, 61 codons are sense codons that code for amino acids, while 3 are stop codons.
• Since there are 20 amino acids, most amino acids are coded by more than one codon.

2. Universal Code

• The genetic code is universal across all living organisms, meaning that the same codons specify the same amino acids in nearly all life forms.

3. Degeneracy of the Code

• The genetic code is degenerate, meaning one amino acid can be coded by multiple codons. For example, serine is coded by UCU, UCC, UCA, and UCG.

4. Commaless Code

• The genetic code is continuous and does not contain punctuation between codons. Each codon is read sequentially, with no gaps in between.

5. Non-Overlapping Code

• Codons are read in groups of three nucleotides, and a single nucleotide cannot be part of more than one codon. For instance:
  • Serine: 5′-UCU-3′
  • Methionine: 5′-AUG-3′

6. Start and Stop Codons

• Start Codon: AUG is the universal start codon and codes for methionine, marking the beginning of protein synthesis.
• Stop Codons: UAA, UAG, and UGA are stop codons that do not code for any amino acid and signal the termination of protein synthesis.

7. Polarity

• Codons are read in a specific direction, from 5′ to 3′. The first base is at the 5′ end, the middle base is next, and the last base is at the 3′ end.
• This polarity ensures that codons are read correctly. Reversing the reading order would alter the base sequence and lead to incorrect protein formation.

What are the Genetic Principles?

The following is the genetic code postulates:

AUG – a codon that initiates a strand of DNA.
In most cases, a single amino acid is associated with multiple mRNA codons in the genetic code. The first two nucleotides in one codon of one amino acid are identical, and the third is different.
The genetic code is made up of three parts. Codon refers to an mRNA triplet.
Codon stops are UAG, UAA, and UGA.
The nucleotide sequence is visible only one way, three times per triplet.
All living things have the same genetic code.

Modification of Genetic Codes

Not all people are the same. In fact, some parts have been found to disappear. Genetic codes are altered and erased during recording and duplication, leading to this condition. Different parts of the DNA are changed and released during the process, leading to mutations.

At that point, genes are discovered and lost, leading to new physiological features in living organisms. Consider the following scenario. Sickle cell anemia is a blood disorder that occurs when the amino acid valine (Val) is replaced by the amino acid glutamine (Gln) gene sequence.