Deletions, in the context of genetics and molecular biology, refer to the removal of one or more nucleotide bases from a DNA sequence. Deletions can occur naturally as a result of errors during DNA replication, repair, or recombination, or due to the action of mobile genetic elements such as transposons. Deletions can also be deliberately introduced into a DNA sequence using genetic engineering techniques.
Deletions can have varying effects on the resulting protein or the organism, depending on the location and size of the deletion:
- Frame-shift mutations: If the number of deleted nucleotides is not a multiple of three, the reading frame of the codons in the mRNA will be shifted, leading to a completely different sequence of amino acids in the translated protein. This usually results in a non-functional or truncated protein, which can have severe consequences for the organism.
- In-frame deletions: If the number of deleted nucleotides is a multiple of three, one or more amino acids will be removed from the protein without changing the reading frame. Depending on the location and nature of the deletion, this may have little to no effect on protein function, or it could disrupt the protein structure and function significantly.
- Regulatory region deletions: If a deletion occurs in a regulatory region of a gene, such as the promoter or enhancer, it may affect the gene’s expression level or the timing of expression.
- Intergenic deletions: If a deletion occurs between genes, it may have no apparent effect, or it could potentially disrupt regulatory elements or non-coding RNA genes.
In genetic engineering, deletions can be used to study gene function by creating “knockout” organisms or cell lines with specific genes removed. This can help researchers understand the role of a particular gene in an organism’s development, physiology, or disease. Various techniques, including CRISPR-Cas9, TALENs, and zinc-finger nucleases, allow for the precise targeting of specific genomic locations to create deletions in the DNA sequence.
