The key difference between transcription and translation is that transcription refers to the process of producing a mRNA molecule for the DNA of a gene while translation refers to the process of synthesizing an amino acid sequence from the transcribed mRNA molecule.
Genes are the units of heredity. Simply they are fragments of DNA. They contain the genetic information (genetic code) to make proteins. In order to produce proteins, they undergo gene expression. Hence, gene expression is the process of synthesizing a protein molecule (gene product) from the genetic information hidden in the gene. Gene expression occurs via two major steps such as transcription and translation. Transcription is the first step, and it is followed by the translation, which is the second major step of gene expression.
CONTENTS
1. Overview and Key Difference
2. What is Transcription
3. What is Translation
4. Similarities Between Transcription and Translation
5. Side by Side Comparison – Transcription vs Translation in Tabular Form
6. Summary
What is Transcription?
Transcription is the first step of the gene expression. It is the process of producing a mRNA molecule from a DNA template. Transcription occurs inside the nucleus of eukaryotes. It is an enzyme-catalyzed reaction. RNA polymerase is the enzyme which catalyzes this process. Among the two strands of DNA in a gene, one serves as the coding sequence while the other is the non-coding sequence.
Non-coding sequence serves as the template in transcription since it is complementary to the coding sequence. RNA polymerase enzyme reads the nucleotides of the coding sequence and adds correct complementary ribonucleotides and constructs the mRNA molecule, which contains the genetic code of the coding sequence. Hence, the resulting mRNA sequence becomes identical to the coding sequence. However, since it is an RNA sequence, RNA polymerase adds uracil instead of thymine during the transcription.
Figure 01: Transcription
In prokaryotes, only a single type of RNA polymerase catalyzes the transcription. But in eukaryotes, three types of RNA polymerases (I, II and II) carry out the transcription. Furthermore, a promoter sequence is essential to initiate the transcription and transcription terminates when the RNA polymerase meets the terminator sequence.
What is Translation?
Translation is the second step of gene expression. Moreover, it is the process of converting mRNA molecule into an amino acid sequence of a protein. It occurs in the cell organelle called ribosomes present in the cytoplasm of the cell. The hidden genetic information in mRNA molecule is the order of the amino acid sequence of the protein that codes by the gene. Structurally, three nucleotides collectively constitute a codon.
Figure 02: Translation
One codon specifies a specific amino acid out from the total of 20 amino acids. Accordingly, the specified amino acid sequence is synthesized from the mRNA molecule during the translation process. Moreover, translation occurs via three phases namely initiation, elongation and termination. At the end of the termination phase, ribosome releases the peptide chain of the protein.
What are the Similarities Between Transcription and Translation?
- Transcription and Translation are major steps of gene expression.
- mRNA involves with both processes.
- Also, both are similarly essential for protein synthesis.
- Furthermore, both processes have three major phases.
- Moreover, both processes need a template to initiate.
What is the Difference Between Transcription and Translation?
Transcription and translation are two different steps of gene expression. We can identify the difference between transcription and translation based on several factors such as a template, raw material, location, product, enzymes involved, etc. Primarily, transcription is the process of producing a mRNA molecule from a DNA template of a gene. On the other hand, translation is the process of producing an amino acid sequence of a protein from a mRNA molecule. Therefore, this is the key difference between transcription and translation.
Furthermore, based on the raw material, the difference between transcription and translation is that transcription requires four types of ribonucleotides as its raw materials while translation requires 20 different amino acids as its raw materials. Similarly, transcription occurs in the nucleus while translation occurs in the ribosomes. Hence, this is the difference between transcription and translation in relation to the location of occurence. More differences between transcription and translation are shown in the below infographic.
Summary – Transcription vs Translation
Transcription and translation are two main steps of the gene expression process. Transcription is followed by the translation. In other words, translation uses the product of transcription. Therefore, unless both these steps are completed, the gene expression process remains incomplete. During the transcription, the information in the coding sequence transfers into a mRNA molecule while during the translation, codons in the mRNA molecule convert into an amino acid sequence of a protein. This is the major difference between transcription and translation. Furthermore, transcription occurs inside the nucleus of eukaryotes while transcription occurs in the cytoplasm associated with ribosomes.
Reference:
1.Nature News, Nature Publishing Group. Available here
2.Nature News, Nature Publishing Group. Available here
Image Courtesy:
1.”Simple transcription elongation1″By Forluvoft – Own work, (Public Domain) via Commons Wikimedia
2.”Protein synthesis”By Kelvinsong – Own work, (CC BY 3.0) via Commons Wikimedia