Expert reviewed • 08 January 2025 • 6 minute read
Our genome consists of both coding and non-coding DNA. While coding regions directly produce proteins, non-coding regions play essential regulatory and structural roles. Mutations in either area can significantly affect an organism’s biology, health, and evolutionary trajectory.
Only around 1.5% of the human genome encodes proteins, leaving approximately 98.5% as non-coding DNA. Although once considered "junk," non-coding regions are now known to be integral in regulating when, where, and how genes are expressed.
Genome composition overview:
Mutations within coding regions can alter the amino acid sequence of proteins, sometimes resulting in severe phenotypic effects. For instance, a single base substitution can change an amino acid, truncate the protein, or shift the reading frame.
| Mutation Type | Effect on Protein | Example Disease |
|---|---|---|
| Missense | Wrong amino acid inserted | Sickle cell anaemia |
| Nonsense | Premature stop codon | Some cystic fibrosis cases |
| Frameshift | Altered reading frame | Tay-Sachs disease |
A classic example is the mutation in the haemoglobin gene leading to sickle cell anaemia, where a single base change has profound effects on the protein’s shape and function.
Non-coding DNA includes regulatory elements such as promoters, enhancers, and silencers that control gene activity. It also encompasses structural components like telomeres and centromeres, as well as genes for functional RNAs (tRNA, rRNA, and miRNA) that guide protein synthesis or regulate gene expression.
Mutations in non-coding regions can subtly alter gene expression levels, timing, and location. Such changes can be minimal or severe, influencing traits, development, and disease risks. For example, certain thalassaemia cases result from promoter mutations, and enhancer alterations have been linked to various developmental disorders.
Introns, the non-coding segments within genes, are not simply "spacers." They regulate alternative splicing, control gene expression, and contribute to the evolution of new genes. Mutations in introns can disrupt normal splicing, activate cryptic splice sites, and alter gene expression levels, potentially causing disease.
Advanced tools such as whole genome sequencing, functional genomics, comparative genetics, and CRISPR technology allow researchers to study both coding and non-coding mutations more comprehensively. This knowledge improves:
Realising that both coding and non-coding DNA mutations matter deepens our understanding of genetic disorders, evolution, biotechnology, and gene-based therapies. As research progresses, it will inform new approaches to disease management, genetic engineering, and the study of biodiversity.