Why are frameshift mutations likely to be more detrimental than point mutations, in which a single pyrimidine or purine has been substituted?

Verified step by step guidance

1. Understand the nature of point mutations: these involve the substitution of a single nucleotide base (a purine or pyrimidine) with another, which may or may not change the amino acid sequence due to the redundancy of the genetic code.
2. Recognize that frameshift mutations occur when nucleotides are inserted or deleted in numbers not divisible by three, causing a shift in the reading frame of the mRNA during translation.
3. Analyze how the reading frame shift alters the grouping of codons downstream of the mutation, potentially changing every amino acid encoded after the mutation site.
4. Consider the consequences of this shift: it often leads to the production of a completely different and usually nonfunctional protein, or introduces premature stop codons that truncate the protein.
5. Compare this to point mutations, which may only affect a single amino acid or sometimes have no effect at all (silent mutations), explaining why frameshift mutations are generally more detrimental.

Key Concepts

Frameshift Mutations

Frameshift mutations occur when nucleotides are inserted or deleted from the DNA sequence, altering the reading frame of the gene. This shift changes every codon downstream, often resulting in a completely different and nonfunctional protein. Because the entire amino acid sequence is affected, frameshift mutations tend to have severe consequences.

Point Mutations

Point mutations involve the substitution of a single nucleotide base, such as replacing one purine or pyrimidine with another. These mutations may cause a silent, missense, or nonsense change, often affecting only one amino acid or sometimes none, making their impact generally less severe than frameshift mutations.

Genetic Code and Reading Frame

The genetic code is read in triplets called codons, each coding for a specific amino acid. Maintaining the correct reading frame is crucial for producing functional proteins. Frameshift mutations disrupt this frame, while point mutations usually do not, explaining why frameshifts are more detrimental.