What term describes changes in a single nucleotide in a DNA sequence?

What term describes changes in a single nucleotide in a DNA sequence?

• A. Point mutations
• B. Frameshift mutation
• C. Inversion mutation
• D. Plastids

Answer: (A)

Point mutations are changes in a single nucleotide base in the DNA sequence. This typically means a base substitution, where one nucleotide is replaced by another, such as an adenine being swapped for guanine. Such a change can alter the codon and, depending on the new codon, may change which amino acid is added during protein synthesis (missense), create a premature stop signal (nonsense), or still code for the same amino acid (silent). The key idea is that the alteration is at only one nucleotide position, unlike mutations that involve larger changes like insertions or deletions that shift the reading frame, or inversions where a segment flips. Plastids are unrelated to DNA sequence mutations, so they don’t describe this concept. Understanding point mutations helps explain how a tiny change at a single spot in the genome can have varying effects on a protein and phenotype.

Point mutations are changes in a single nucleotide base in the DNA sequence. This typically means a base substitution, where one nucleotide is replaced by another, such as an adenine being swapped for guanine. Such a change can alter the codon and, depending on the new codon, may change which amino acid is added during protein synthesis (missense), create a premature stop signal (nonsense), or still code for the same amino acid (silent). The key idea is that the alteration is at only one nucleotide position, unlike mutations that involve larger changes like insertions or deletions that shift the reading frame, or inversions where a segment flips. Plastids are unrelated to DNA sequence mutations, so they don’t describe this concept. Understanding point mutations helps explain how a tiny change at a single spot in the genome can have varying effects on a protein and phenotype.