Consequences of Insertions and Deletions
- Insertions add extra nucleotides into the DNA sequence.
- Deletions remove nucleotides from the DNA sequence.
- Both disrupt the genetic code, often with severe consequences.
Frameshift Mutations: A Domino Effect
- DNA is read in triplets called codons, each coding for a specific amino acid.
- Inserting or deleting a nucleotide shifts the reading frame, altering every codon downstream.
- Frameshifts are not the same as substitutions.
- Substitutions affect only one codon, while frameshifts disrupt the entire sequence.
If the insertion or deletion occurs near the start of the gene, the effects are usually more severe because most of the protein is altered.
Major Insertions and Deletions: Structural Chaos
- Larger insertions or deletions (multiples of three) don’t cause frame shifts but still disrupt protein function.
- They add or remove entire amino acids, altering the protein’s shape and stability.
- Imagine a zipper missing several teeth.
- It might still work, but not as efficiently or reliably.
Consequences of Major Changes
- Loss of Function: The protein may become unstable or unable to bind to other molecules.
- Gain of Function: Rarely, these mutations create new functions, but they are usually harmful.
Even if the reading frame is preserved, the addition or removal of amino acids can disrupt critical regions of the protein, such as active sites or binding domains.
