Final answer:
Point mutations may not affect an organism if they result in a silent mutation, where the new codon codes for the same amino acid as the original. Silent mutations do not change the protein product, thus having no effect on the organism's phenotype.
Step-by-step explanation:
Point mutations may have no effect on an organism if the new codon codes for the same amino acid as the original codon. This type of mutation is known as a silent mutation, and it occurs because the genetic code is redundant, allowing multiple codons to code for the same amino acid. The redundancy in the genetic code often preserves the amino acid sequence of a protein despite a mutation in the DNA sequence. Silent mutations do not alter the protein that is produced, therefore having no effect on the organism's phenotype.
In contrast, a missense mutation occurs when a point mutation results in a different amino acid being placed in a protein. This can potentially affect the protein's function, especially if the new amino acid has different chemical properties or is located in a critical area such as the active site of an enzyme. However, if the new amino acid is chemically similar to the original, the change might not significantly impact protein function.
Ultimately, not all point mutations are deleterious. Some may result in a neutral effect or, in rare cases, may even confer an advantage to the organism under certain environmental conditions.