What is the Difference Between Coding and Non-coding RNA

Understanding the basic differences between coding and non-coding RNA is important for unraveling genetic regulation and its effects on various biological processes. In this article, we dive into this aspect of molecular biology, aiming to explain the distinct roles and functions of these RNA types in a clear and straightforward manner.

The key difference between coding and non-coding RNA is their function. Coding RNA is an RNA molecule that encodes for a protein, while non-coding RNA is an RNA molecule that is not translated into a protein.

CONTENTS

1. Overview and Key Difference
2. What is Coding RNA
3.  What is Non-coding RNA
4. Similarities – Coding and Non-coding RNA
5. Coding vs Non-coding RNA in Tabular Form
6. Summary – Coding vs Non-coding RNA
7. FAQ: Coding and Non-coding RNA

What is Coding RNA?

Coding RNA, also known as messenger RNA, carries the genetic code from DNA in a form that can be recognized to produce a protein. Normally, the coding sequence of the mRNA determines the amino acid sequence in a protein. In eukaryotic organisms, once transcribed from DNA, mRNA briefly exists as a precursor mRNA molecule before turning into mature mRNA. This step is known as RNA splicing.

During RNA splicing, introns are removed, and exons are joined in order to form the mature mRNA molecule. Furthermore, there are approximately 23,000 coding RNAs encoded in the human genome.

What is Non-coding RNA?

Non-coding RNA is an RNA molecule that does not code for a protein. There are different abundant and functionally important types of non-coding RNAs, such as transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs), small non-coding RNAs such as microRNAs, siRNAs, snoRNAs, snRNAs, piRNAs, exRNAs, scaRNAs and the long non-coding RNAs such as  Xist and HOTAIR.

About 80% of the transcriptome of humans consists of non-coding RNA. They are one of the components of epigenetic mechanisms of regulation of gene expression. Non-coding RNA plays a major role in the development and functioning of the brain as well. Furthermore, non-coding RNA is also involved in the pathogenesis of psychiatric disorders.

Similarities Between Coding and Non-coding RNA

1. Coding and non-coding RNA are two different types of RNA molecules in the body.
2. Both are functional molecules.
3. Both molecules have ribose sugars attached to nitrogenous bases and phosphate groups.
4. They have adenine, guanine, uracil, and cytosine as nitrogen bases.

Comparing the Difference Between Coding and Non-coding RNA

Definition

1. Coding RNA is an RNA that carries the genetic code from DNA in a form that can be recognized to produce a protein.
2. Non-coding RNA is an RNA molecule that does not encode a protein.

Amount

1. Coding RNA comprises 20% of the transcriptome by mass.
2. Non-coding RNA comprises 80% of the transcriptome by mass.

Single or Double-stranded

1. Coding RNA is single-stranded.
2. Non-coding RNA is single or double-stranded.

Function

1. The function of coding RNA is to encode a protein.
2. The functions of non-coding RNA include protein translation regulation, antiviral defense, regulation of transposable elements, intron splicing, rRNA processing, components of ribonucleoprotein, protein scaffolding, RNAi, alternate splicing, genome imprinting, miRNA decoy, protein regulation, epigenetic mechanisms of regulation of gene expression. Non-coding RNA plays a major role in the development and functioning of the brain and is also involved in the pathogenesis of psychiatric disorders.

The infographic below presents the differences between coding and non-coding RNA in tabular form for side-by-side comparison.

Summary – Coding vs. Non-coding RNA

RNA or ribonucleic acid is a nucleic acid present in all living cells. Coding and non-coding RNA are two different types of RNA molecules in the body. A coding RNA encodes for a protein, while non-coding RNA is not translated into a protein. Moreover, coding RNA comprises 20 % of the transcriptome by mass. On the other hand, non-coding RNA comprises 80 % of the transcriptome by mass. Thus, this is the summary of the difference between coding and non-coding RNA.

FAQ: Coding and Non-coding RNA

1. What is non-coding RNA and its importance?

1. 1. • Non-coding RNA refers to the category of RNA that does not translate directly into a protein. However, non-coding RNA are important because they are involved in different functions within the cell, including hetero-chromatin formation, histone modification, DNA methylation, etc.

2. Is tRNA a non-coding RNA?

1. 1. • tRNA is a type of non-coding RNA that is very important in the process of protein synthesis. When recruiting an amino acid in order to grow the amino acid chain, tRNA pairs with the mRNA sequence at the correct position and ensures the insertion of the correct amino acid for the chain. Therefore, it involves carrying the correct amino acid to the ribosomes.

3. How do you know if RNA is non-coding?

1. 1. • CNCI analysis (Coding-Non-Coding Index) is one of the methods of identifying non-coding RNA from coding RNA. It identifies non-coding RNA by the traits of adjacent nucleotide triplets, effectively predicting incomplete transcripts and antisense transcripts.

4. What are the non-coding RNA examples?

1. 1. 1. There are several types of non-coding RNA. Some of them are micro RNAs (miRNAs), ribosomal RNAs, transfer RNAs, small nucleolar RNAs (snow RNAs), and small nuclear RNAs (snRNAs). Though they do not translate into proteins, they serve different functions in living organisms.

5. How much RNA is non-coding?

1. 1. • Non-coding RNA accounts for a large portion of the transcriptome. In other words, around 98% of transcriptomes are non-coding RNA. In the human genome, 5% is non-protein-coding DNA sequences that are transcribed into RNA.

Reference:

1. Dinger, Marcel E., et al. “Differentiating Protein-Coding and Non-coding RNA: Challenges and Ambiguities.” PLOS Computational Biology, Public Library of Science.
2. “Non-Coding RNA – An Overview.” ScienceDirect Topics.

Image Courtesy:

1. “Peptide syn” By Boumphreyfr vector conversion by Glrx – File:Peptide syn.png (CC BY-SA 3.0) via Commons Wikimedia
2. “An atlas of human long non-coding RNAs with accurate 5’ ends” By Hon C – Fantom GSC  (CC BY-SA 4.0) via Commons Wikimedia