What are point mutations and insertions/deletions (indels)?

What are point mutations and insertions/deletions (indels)?

• A. Point mutations change amino acids; indels do not affect reading frames.
• B. Point mutations substitute a single base; indels add or remove bases, causing frameshifts.
• C. Point mutations remove entire genes; indels insert entire genes.
• D. Point mutations always silent; indels always cause stop codons.

Answer: (B)

Point mutations are substitutions of a single nucleotide in the DNA. They change one base within a codon, so the codon can still code for the same amino acid (silent), code for a different amino acid (missense), or become a stop signal (nonsense). Insertions and deletions (indels) are additions or losses of nucleotides. They disrupt how codons are read because codons are read in groups of three bases. If the indel is not a multiple of three bases, the reading frame shifts from that point onward (frameshift), usually scrambling downstream amino acids and often creating a premature stop. If the indel length is a multiple of three, the reading frame is preserved, adding or removing whole amino acids without shifting downstream codons. So, a single-base change is a point mutation; indels add or remove bases and can cause a frameshift.

Point mutations are substitutions of a single nucleotide in the DNA. They change one base within a codon, so the codon can still code for the same amino acid (silent), code for a different amino acid (missense), or become a stop signal (nonsense). Insertions and deletions (indels) are additions or losses of nucleotides. They disrupt how codons are read because codons are read in groups of three bases. If the indel is not a multiple of three bases, the reading frame shifts from that point onward (frameshift), usually scrambling downstream amino acids and often creating a premature stop. If the indel length is a multiple of three, the reading frame is preserved, adding or removing whole amino acids without shifting downstream codons. So, a single-base change is a point mutation; indels add or remove bases and can cause a frameshift.