TRANSLATION OF DNA

 INTRODUCTION TO TRANSLATION OF DNA

Translation is the process by which the genetic code contained within a messenger RNA (mRNA)
molecule is decoded to produce a specific sequence of amino acids in a polypeptide chain. It occurs
in the cytoplasm following DNA transcription and, like transcription, has three stages: initiation,
elongation, and termination. In this article, we will discuss the components and stages of DNA
translation.

Figure 1 TRANSLATION OF DNA

 COMPONENTS INVOLVED IN DNA TRANSLATION

The key components required for translation are mRNA, tRNA, ribosomes, and aminoacyl tRNA
synthetizes.

1. RIBOSOME

The ribosome is a complex organelle, present in the cytoplasm, which serves as the site of action
for protein synthesis. It provides the enzymes needed for peptide bond formation. The nucleotide
sequence in mRNA is recognized in triplets, called codons. The ribosome moves along the single
strand mRNA, and when a complimentary codon sequence belonging to amino acid bearing tRNA
bonds with the mRNA, the amino acid is added to the chain.

2. MESSENGER RNA (mRNA)

mRNA is used to convey information from DNA to the ribosome. It is a single strand molecule,
complimentary to the DNA template, and is generated through transcription. Strands of mRNA
are made up of codons, each of which signifies a particular amino acid to be added to the
polypeptide in a certain order. mRNA must interact with ribosomal RNA (rRNA), the central
component of ribosomal machinery that recognizes the start and stop codons of mRNA, and tRNA,
which provides the amino acid once bound with a complimentary mRNA codon.

3. TRANSFER RNA (tRNA)

This is a single strand of RNA composed of approximately 80 ribonucleotides. Each tRNA is read
as a ribonucleotide triplet called an anticodon that is complementary to an mRNA codon. tRNA
carry a particular amino acid, which is added to the growing polypeptide chain if complimentary
codons bond.

Figure 2 STRUCTURE OF tRNA MOLECULE

These are enzymes that link each amino acid to their corresponding tRNA with the help of a two-
step process. Each amino acid has a unique synthetize and the active site of each enzyme fits only
one specific combination of the amino acid and tRNA.

 STEPS INVOLVED IN DNA TRANSLATION

There are three major steps in translation: initiation, elongation, and termination.

1. INITIATION

Translation begins with the assembly of the components necessary for protein synthesis:

a. mRNA Binding: The small ribosomal subunit binds to the mRNA near its 5' end,
recognizing a specific sequence upstream of the start codon (AUG).
b. Initiator tRNA Binding: The initiator tRNA carrying methionine (tRNA^Met) binds to the
start codon (AUG) on the mRNA. The anticodon of the tRNA pairs with the start codon.
c. Ribosome Assembly: The large ribosomal subunit binds to the small subunit, forming a
complete ribosome with the initiator tRNA positioned in the P site (peptidyl site).

Figure 3 TRANSLATION INITIATION

During elongation, the ribosome travels along the mRNA, synthesizing the polypeptide chain:

a. Codon Recognition: A tRNA with an anticodon complementary to the next mRNA codon
binds to the A site (aminoacyl site) of the ribosome, bringing the appropriate amino acid.
b. Peptide Bond Formation: The ribosome catalyzes the formation of a peptide bond between
the amino acid attached to the tRNA in the P site and the new amino acid in the A site.
c. Translocation: The ribosome moves (translocates) one codon along the mRNA. This shifts
the tRNA in the P site to the E site (exit site), and the tRNA in the A site to the P site.
d. Exit of Empty tRNA: The tRNA in the E site, now without an amino acid, is released from
the ribosome.
e. Repeat: The cycle repeats, with new tRNAs bringing amino acids to the A site, elongating
the polypeptide chain.

Figure 4 ELONGATION PROCESS

3. TERMINATION

Elongation continues until a stop codon (UAA, UAG, or UGA) is encountered on the mRNA:
 a. Stop Codon Recognition: No tRNA matches the stop codons. Instead, release factors
(proteins) bind to the stop codon in the A site.
b. Release of Polypeptide: The release factors trigger the ribosome to cleave the polypeptide
chain from the tRNA in the P site.
c. Ribosome Disassembly: The ribosome dissociates into its large and small subunits,
releasing the mRNA and the newly synthesized polypeptide, which will undergo folding
and post-translational modifications to become a functional protein.

Figure 5 TERMINATION OF TRANSLATION

 CONCLUTION

The translation of DNA into proteins is a fundamental biological process that ensures the genetic
information stored in DNA is accurately expressed as functional proteins. This multi-step process
involves the precise orchestration of transcription, translation initiation, elongation, and
termination. Transcription converts DNA into mRNA, which then guides the synthesis of proteins
in the cytoplasm. Initiation marks the assembly of the translation machinery, while elongation
involves the step-by-step addition of amino acids to the growing polypeptide chain, dictated by
the sequence of codons on the mRNA. Termination occurs when a stop codon is reached,
prompting the release of the completed polypeptide and disassembly of the ribosomal units. Key
components in this process include mRNA, ribosomes, tRNA, aminoacyl-tRNA synthetizes, and
release factors. Each component plays a crucial role in ensuring the fidelity and efficiency of
protein synthesis, which is essential for maintaining cellular functions and overall organism health.
Understanding the translation process not only provides insights into basic biological mechanisms
but also has significant implications for fields such as genetics, biotechnology, and medicine.
Errors in translation can lead to diseases, while targeted manipulation of this process can lead to
advances in genetic therapies and synthetic biology. Thus, the translation of DNA is not only a
marvel of biological engineering but also a cornerstone of life itself.