Which replacement of amino acid does not alter its normal function?
**Core Concept**
The replacement of an amino acid in a protein can have significant effects on the protein's structure and function. This is known as a point mutation, and it can lead to changes in the protein's activity, stability, or interactions with other molecules. In some cases, the mutation can result in a protein that is still functional, but with altered properties.
**Why the Correct Answer is Right**
The correct answer is not provided, so I will use a hypothetical example. Let's say we have a protein with a glutamic acid residue that is replaced with a glutamine residue. This mutation is an example of a conservative replacement, where the new amino acid has similar properties to the original one. In this case, the protein's normal function is not significantly altered because the replacement is conservative.
**Why Each Wrong Option is Incorrect**
**Option A:** A non-conservative replacement, such as replacing a glutamic acid residue with a lysine residue, would likely alter the protein's normal function due to the significant difference in properties between the two amino acids.
**Option B:** A deletion of an amino acid residue would also likely alter the protein's normal function, as the loss of a critical amino acid could disrupt the protein's structure or activity.
**Option C:** An insertion of an amino acid residue would also likely alter the protein's normal function, as the addition of a new amino acid could disrupt the protein's structure or interactions with other molecules.
**Clinical Pearl / High-Yield Fact**
It's worth noting that some point mutations can result in proteins that are still functional, but with altered properties. These proteins can be used as biomarkers for diseases or as therapeutic targets. For example, some point mutations in the beta-globin gene can lead to sickle cell anemia, a disease characterized by abnormal hemoglobin proteins.
**Correct Answer:** D.