In a mutation if valine is replaced by which of the following would not result in any change in the function of protein:
**Core Concept**
Mutations in DNA can lead to changes in amino acid sequences of proteins, potentially altering their function. However, some amino acid substitutions may not significantly impact protein function due to similar physical and chemical properties. This is particularly relevant when the substitution occurs in a non-critical region of the protein.
**Why the Correct Answer is Right**
The correct answer is **glutamic acid**. This is because valine and glutamic acid have similar side chain properties, with valine being non-polar and hydrophobic, while glutamic acid is polar and hydrophilic. However, glutamic acid is negatively charged, whereas valine is not. Nevertheless, this charge difference is often not critical in protein function, especially in regions that are not involved in substrate binding or enzymatic activity. The similarity in side chain properties between valine and glutamic acid makes this substitution less likely to result in a significant change in protein function.
**Why Each Wrong Option is Incorrect**
**Option A:** **Leucine**. Leucine is another non-polar, hydrophobic amino acid, but it has a larger side chain than valine, which may alter the protein's structure and function.
**Option B:** **Asparagine**. Asparagine is a polar amino acid, which differs significantly from the non-polar valine. This substitution could alter the protein's function, particularly if the asparagine residue is involved in hydrogen bonding or other interactions.
**Option C:** **Lysine**. Lysine is a positively charged amino acid, which is distinct from the non-polar valine. This substitution could significantly alter the protein's function, particularly if the lysine residue is involved in electrostatic interactions.
**Clinical Pearl / High-Yield Fact**
When considering the effects of amino acid substitutions on protein function, it's essential to evaluate the location of the substitution within the protein sequence and the potential impact on the protein's structure and interactions.
**Correct Answer:** B. Asparagine.