Question

List four ways that DNA can mutate without affecting the phenotype.

Short answer

DNA can mutate without affecting the phenotype in the following ways: 1) silent mutations, 2) mutations in the non-coding regions of DNA, 3) mutations occurring in the third position of a codon, and 4) same-sense mutations.

Step-by-step solution

Silent mutations

Silent mutations are changes in the DNA sequence which do not change the amino acid that is produced during protein synthesis. This is because several different codons can specify the same amino acid. For example, the codons GCU, GCC, GCA, and GCG all code for the amino acid alanine. Therefore, a change from GCU to GCC would not alter the phenotype.

Mutations in non-coding regions

The non-coding regions of the DNA (regions that do not code for proteins) contain a significant portion of the entire genetic sequence of an organism. Mutations in these regions generally do not affect the phenotype as they do not change the protein-coding sequence.

Mutations involving third positions in a codon

A mutation that occurs in the third position of a codon might not affect the phenotype of the organism. This is due to the 'wobble' effect, where the base in the third position of a codon can vary and still code for the same amino acid.

Same-sense mutations

These mutations involve a change which swaps one codon for another, but the new codon still codes for the same amino acid, hence no phenotypical change occurs.