Our bodies are made of cells, and within each cell lies our DNA, a detailed instruction manual for life. This DNA is organized into genes, which contain the specific codes needed for our bodies to grow, develop, and function properly. Sometimes, changes occur in these DNA sequences. These alterations are known as genetic mutations. While mutations can vary widely in their nature and impact, they are a natural part of the genetic landscape.
Defining Indel Mutations
A genetic mutation involving the gain or loss of small DNA segments is known as an indel mutation. The term “indel” is a portmanteau, combining “insertion” and “deletion.” An insertion involves the addition of one or more base pairs into a DNA sequence, while a deletion refers to the removal of one or more base pairs from the sequence.
Indels within the 1 to 50 base pair range are relatively small changes to the genetic code. For instance, imagining a sentence as a DNA strand, an insertion would be like adding a few extra letters into a word, while a deletion would be like removing a few letters. These additions or removals can have significant consequences, depending on where they occur. Indels larger than 50 base pairs are classified as structural variants.
How Indels Alter Genetic Information
The consequences of indel mutations on gene function and protein production depend on their size and location. When an indel involves a number of base pairs that is not a multiple of three, it leads to a “frameshift mutation.” DNA is read in groups of three base pairs, known as codons, with each codon specifying an amino acid, the building blocks of proteins.
A frameshift mutation disrupts this reading frame, much like removing or adding a single letter in a sentence shifts all subsequent letters, making the rest of the sentence nonsensical. This alteration can lead to the production of a completely different, non-functional, or a prematurely truncated protein. Conversely, if an indel involves a multiple of three base pairs, it results in a “non-frameshift mutation.” While this still leads to the gain or loss of specific amino acids, the overall reading frame remains intact, increasing the chance that the protein retains some or full functionality.
Impact on Health and Disease
Indel mutations contribute to the development of various genetic disorders. The specific disease and its severity are determined by the exact location of the indel within a gene and the extent of the change it causes to the protein. For example, cystic fibrosis can result from a small deletion of three base pairs in the CFTR gene.
This deletion leads to the loss of a single amino acid in the CFTR protein, impairing its function in chloride ion transport and affecting various organs, especially the lungs and digestive system. Understanding these specific indel mutations is important for diagnosing genetic conditions and developing targeted therapies. The study of indels helps researchers uncover the underlying causes of many diseases.