Key Difference – Exome vs Transcriptome
A gene contains coding and non-coding regions within it. Coding sequences are known as exons, and non-coding sequences are known as introns. The nucleotide sequence of the exons of a gene represents the genetic code of the gene to synthesize the specific protein. Hence, exons remain in the mRNA molecule. The total exon region of the genome is known as exome, and it is an important part of the genome. The genetic code of the genes is converted into the genetic code of the mRNA molecule, which is needed for the production of protein. The entire mRNA molecules transcribed in a cell or a cell population at a time is known as a transcriptome. The key difference between exome and transcriptome is that exome represents the sequences of the exon regions of the genome while transcriptome represents the total mRNA of a cell or a tissue at a given time.
CONTENTS
1. Overview and Key Difference
2. What is Exome
3. What is Transcriptome
4. Side by Side Comparison – Exome vs Transcriptome
5. Summary
What is Exome?
Genes are composed of exons, introns and regulatory sequences. Exons are the gene regions which are transcribed into mRNA sequence during the transcription. Introns and other non-coding regions are removed during the transcription. The nucleotide sequence of exons determines the genetic code of the gene which synthesizes the specific protein it codes. Only exons remain within mRNA of a protein. The collection of exons in the genome is known as exome of an organism. It represents a part of the genome which is expressed in genes. In humans, exome accounts 1% from the genome. It is the protein-coding portion of the human genome.
Figure 01: Exome
What is Transcriptome?
The transcriptome is the collection of all protein-coding and non-coding transcripts (RNAs) in a given tissue. Transcriptome represents the collection of total mRNA molecules expressed by the genes in a cell or a tissue. The transcriptome of a cell can be varied with the transcriptome of another cell type. The transcriptome is also dynamic – it changes with time in response to both internal and external stimuli. Even within the same tissue or within the same cell type, transcriptome can change after few minutes.
Transcriptome differs from exome of an organism. Transcriptome includes only the expressed exome sequences. Though the exome of a cell remains the same, transcriptome differs among cells since gene expression is not same for all cells or tissues. Only essential genes are expressed in different cells and tissues. Gene expression is a tissue or cell type specific process. It is regulated by various factors including environmental factors. Therefore, transcriptome can vary with external environmental conditions.
Transcriptome is used as a precursor for proteomics studies. All proteins are derived from mRNA sequences. Translational modifications can result in the changes in proteins. However, transcriptome provides important basic information for the proteomic studies.
Figure 02: Transcriptome of embryonic stem cells
What is the difference between Exome and Transcriptome?
Exome vs Transcriptome |
|
| Exome is the collection of protein-coding region of the genes. | Transcriptome is the collection of all transcribed RNA including mRNA. |
| Sample | |
| Exome is studied using DNA sample. | Transcriptome is studied using an RNA sample. |
| Study Method | |
| Whole exome sequencing is the method of studying exome. | RNA sequencing is the method of studying transcriptome. |
Summary – Exome vs Transcriptome
Exons are the coding sequences of the genes and determine the mRNA sequences of the proteins. The collection of these coding sequences (exons) is known as exome of an organism. Genes are transcribed into mRNA molecules prior to making proteins. The total mRNA molecules of a cell or a tissue at any given time are known as transcriptome. Transcriptome represents the genes that are being actively expressed into mRNA at any given time. Transcriptome is cell and tissue specific and affects with the environmental conditions. This is the difference between exome and transcriptome.
References:
1.Sarah et al, “Targeted Capture and Massively Parallel Sequencing of Twelve Human Exomes.” Nature. U.S. National Library of Medicine, 10 Sept. 2009. Web. 01 Apr. 2017
2.Mutz et al. “Transcriptome analysis using next-generation sequencing.” Elsevier: Article Locator. N.p., Sept. 2012. Web. 01 Apr. 2017
Image Courtesy:
1.”The transcriptome of pluripotent cells” By Grskovic, M. and Ramalho-Santos, M., The pluripotent transcriptome (October 10, 2008), StemBook, ed. The Stem Cell Research Community, StemBook, doi/10.3824/stembook.1.24.1, http://www.stembook.org. – [1] DirectStemBook Figure 2 The transcriptome of pluripotent cells.Grskovic, M. and Ramalho-Santos, M., The pluripotent transcriptome (October 10, 2008), StemBook, ed. The Stem Cell Research Community, StemBook, doi/10.3824/stembook.1.24.1, (CC BY 3.0) via Commons Wikimedia