A kind of mutation that involves the substitution of a single nucleotide by another, without changing the frame of reference of the DNA sequence. In this particular example, the thymine in the codon GAG (codes for glutamic acid) is being substituted by the base adenine, leaving the codon GTG (codes for the amino acid, valine).
The described substitution occurs in the case of the disease, sickle cell anemia that yields abnormal heamoglobin.
A) A deletion removes a base from the DNA sequence. This alters the frame of reference of the mRNA.
B) An insertion involves the addition of a base into the DNA sequence.
D) A silent mutation substitutes a base in such as way that the new codon codes for the same amino acid, conserving the function and structure of the protein; therefore, silent mutations are harmless.
