Final answer:
The statement is true, as point mutations generally refer to changes affecting a single nucleotide, but they can include substitutions, insertions, or deletions. The impact of a point mutation ranges from neutral to significant, depending on the mutation's nature and location in the gene.
Step-by-step explanation:
The statement “Point mutations affect just one nucleotide” is generally true. A point mutation is a change in a single nucleotide in the DNA sequence. However, it's important to note that while the most common type of point mutation is a substitution, where one base is replaced by another, some point mutations can also involve the insertion or deletion of a single base pair. These latter types can result in more significant changes, such as frameshift mutations, which alter the reading frame of the genetic code.
There are several types of point mutations, including silent mutations, which do not change the amino acid sequence of a protein; missense mutations, which change one amino acid for another; and nonsense mutations, which introduce a stop codon into the mRNA sequence, potentially leading to an incomplete protein.
The consequences of a point mutation depend on the location within the gene and the type of mutation. For example, a substitution that changes a codon to encode a different amino acid could affect the function of the resulting protein, while a silent mutation might have no observable effect.