Difference Between CDS and cDNA

The key difference between CDS and cDNA is that CDS or coding sequence is the part of a transcript that is actually translated into protein while cDNA sequence is a DNA sequence derived from the mRNA by reverse transcription.

A gene is a nucleotide sequence which codes for a protein. It consists of different regions as promoter region, transcription initiation site, exons, start codon, introns and stop codon. Therefore, a gene has both coding and noncoding sequences. Coding sequences or CDS refers to the exons and two codons, which are start codon and stop codon. It is the sequence that is actually translated into a protein. In contrast, cDNA is a DNA sequence derived from the mRNA by reverse transcription.

1. Overview and Key Difference
2. What is CDS
3. What is cDNA
4. Similarities Between CDS and cDNA
5. Side by Side Comparison – CDS vs cDNA in Tabular Form
6. Summary

What is CDS?

CDS or coding sequence is a part of a gene which is actually translated into a protein. It comprises of exons and two codons as AUG codon and stop codon. Unlike cDNA, CDS does not contain two untranslated regions: 5’ UTR and 3” UTR. Moreover, introns are not included in CDS.

Figure 01: Coding Sequence

When compared to the whole genome and an individual, coding sequences are a small fraction. Coding sequence consists of the necessary nucleotide sequence to make the amino acid sequence of the protein.

What is cDNA?

cDNA or complementary DNA is a DNA sequence generated from mRNA sequence. It is synthesized by the process called reverse transcription. The enzyme reverse transcriptase catalyzes cDNA synthesis, and mRNA sequence acts as the template for cDNA synthesis. Basically, mRNA of eukaryotic cells can be extracted and purified in order to make cDNA. After constructing cDNA from mRNA, they can then be cloned into a bacterial cell in order to make cDNA libraries. cDNA libraries are important for the analysis of coding regions, gene functions and expression of genes, etc.

Figure 02: cDNA

Unlike coding sequence, cDNA contains two UTRs, which are 3’ UTR and 5’ UTR. Similar to the coding sequence, cDNA does not contain introns.

What are the Similarities Between CDS and cDNA?

CDS and cDNA are nucleic acids.
They are made from deoxyribonucleotides.
Both CDS and CDNA do not contain introns, which are noncoding regions.
Both contain the genetic code or information to produce a protein.

What is the Difference Between CDS and cDNA?

CDS or coding sequence is the part of a gene that is actually translated into a protein. On the other hand, cDNA sequence is a DNA sequence derived from the mRNA by reverse transcription. So, this is the key difference between CDS and cDNA. Besides, CDS consists of exons and two codons, which are start codon and stop codon. In contrast, cDNA consists of the complete mRNA sequence and two UTRs.

Moreover, cDNA synthesis is done artificially from mRNA by reverse transcription while CDS are found in the genomic DNA.

Below infographic shows more comparisons to discern the difference between CDS and cDNA.

Summary – CDS vs cDNA

Coding sequence and cDNA are two types of nucleotide sequences. Coding sequence lies within a gene while cDNA is synthesized artificially. Coding sequence has exons and two codons while cDNA has an mRNA sequence and two UTRs. Both CDS and cDNA have only the nucleotide sequences which actually translate into a protein. They do not contain introns. Unlike CDS, cDNA synthesis process requires reverse transcriptase enzyme. Also, cDNA can convert into cDNA libraries. Thus, this summarizes the difference between CDS and cDNA.

Reference:

1. “Coding Region.” Wikipedia, Wikimedia Foundation, 18 Apr. 2020, Available here.

Image Courtesy:

1. “Coding Region in DNA” By Pragpats – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Formation of a cDNA Library” By PhD Dre at the English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia