Transcription is a DNA template synthesis of RNA where the code in the DNA is translated to a complementary RNA code. Translation is a protein synthesis from an mRNA template where the mRNA code is translated into a series of amino acids in a protein. 

Difference Between Transcription and Translation

Transcription v TranslationIn the process of genetic material flowing within a cell, from genes in DNA to proteins, both transcription and translation are equally significant. Without the other, no process will occur. In these processes, though, there are some significant differences.

Here are the 10 major differences between transcription and translation in the table below:

Particulars  Transcription Translation
Purpose   The purpose of transcription is to create RNA copies of individual genes that can be used by the cell in biochemistry. Translation is intended to synthesize proteins that are used for millions of cellular functions.
Precursor  non-coding or antisense DNA strand mRNA produced from transcription.
Gene expression First step Second and final step 
Occurrence  Before translation After transcription 
Raw materials  4 base pairs of RNA; adenine, uracil, guanine, and cytosine 20 amino acids 
Initiation  It is initiated by the identification of specific DNA sequences named promoter sequences. Translation to the ribosomes is initiated by the binding of mRNA.
Enzymes  DNA-dependent RNA polymerase amino acetyl tRNA synthetase
End Products  mRNA, tRNA, rRNA and non-coding RNA (like microRNA) Proteins 
Antibiotics  inhibited by rifampicin and   8-Hydroxyquinoline. inhibited by anisomycin, chloramphenicol, tetracyclin, cycloheximide, streptomycin, puromycin, and erythromycin. 
Location  Nucleus  Cytoplasm 

 

Transcription

Transcription is the process where a series of polymerization reactions catalyzed by enzymes called DNA-dependent RNA polymerases transfer the genetic material on a DNA strand into an RNA strand. This is the first step of the production of proteins or the information flow within a cell.

Until directing the synthesis of proteins in translation, DNA stores genetic information which is then transmitted to RNA in transcription. It is possible to form three kinds of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). 

Transcription happens in four steps: pre-initiation, initiation, elongation, and termination.

1. Pre-initiation

The RNA polymerase σ subunit bound to a promoter region situated at the 5 ‘end of a DNA strand initiates the pre-initiation or also known as template binding. The DNA strand is denatured after this, uncoupling the two complementary strands and allowing the enzyme to enter the template strand. The opposing strand is identified as a partner strand. Promoter sequences on the DNA strand are important for the efficient initiation of transcription. 

Basic sequences of the ribonucleotide bases that make up the DNA strand (adenine, thymine, guanine, and cytosine) are promoter sequences, and some of these motifs, including TATAAT and TTGACA in prokaryotes and TATAAAA and GGCCAATCT in eukaryotes, have been established. These sequences are known as components of cis-acting. In eukaryotes, to allow the binding of RNA polymerase to the promoter region, an additional transcription factor is required.

2. Initiation

Initiation catalyzes RNA polymerase, triggering the introduction of the first complementary 5′-ribonucleoside triphosphate. Note that there is a complement to each DNA nucleotide base: adenine and thymine, and guanine and cytosine. 

The ribonucleotide base complements, however, vary slightly because RNA does not contain thymine, but rather uracil, and so the complement of adenine is uracil. Subsequent complementary ribonucleotides are added in the direction of 5 ‘to 3′ after the release of the first complementary 5’-ribonucleotide. Phosphodiester bonds join these ribonucleotides, and at this point, the DNA and RNA molecules are still connected.

3. Elongation

As the σ subunit dissociates from the DNA strand, chain elongation occurs, causing the growing RNA strand to differentiate from the DNA template strand. The core enzyme promotes this.

4. Termination

Termination happens when a termination sequence, which is a particular nucleotide sequence that serves as a signal to interrupt transcription, is found by the core enzyme. At this stage, by folding back on itself with the help of hydrogen bonds, the RNA transcript forms a hairpin secondary structure.

An additional termination element known as rho(ρ) will assist termination in prokaryotes. When the RNA molecule is freed from the template DNA chain, termination is complete. In eukaryotes, termination includes an additional step known in eukaryotes as polyadenylation, whereby a tail is attached to the RNA strand of multiple adenosine monophosphates.

Translation

Translation refers to the transfer from one language or process to another of something. Translation is the mechanism in biology by which messenger ribonucleic acid, or mRNA, synthesizes proteins, translating mRNA to proteins.

This is achieved by the manufacture of an amino acid chain (a polypeptide chain) which is determined by the chemical details contained in a particular mRNA strand. These polypeptides fold to build proteins. A different gene codes each strand of mRNA and codes a different protein. For gene expression, this is important.

Translation has three primary stages: initiation, elongation, and termination.

1. Initiation

Two different subunits make up the ribosome: the small subunit and the large subunit. The small subunit binds to the 5- ‘end of mRNA during initiation.  It then moves in the 5’ 3′ direction.  Once the beginning codon (AUG) is struck by the small subunit, the corresponding tRNA is added, followed by the large subunit. The amino acid methionine is always carried by the first tRNA molecule.

2. Elongation

The tRNA with the right corresponding anticodon would fit the corresponding mRNA codon in the elongation step of translation. A peptide bond is formed between the methionine of the first tRNA and the second amino acid of the second tRNA, which is the kind of bond that binds the amino acids together. The ribosome then travels down in the direction of 5 ‘ 3′, allowing a way for another tRNA to match its corresponding codon, causing another peptide bond to form. With the ribosome going down the mRNA strand, this mechanism begins, expanding the amino acid chain the further it goes.

A significant point to remember is that it then leaves the ribosome to be “recharged” with another amino acid until a tRNA moves the amino acid to the amino acid chain.

3. Termination

Termination is the final step of translation. A release factor will bind to the stop codon and allow the amino acid chain to be released and the ribosome subunits to split when the ribosome crosses a stop codon (UAG, UAA, or UGA).

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(Last Updated On: January 15, 2021)