Question

Site directed mutagenesis facilitated research on

• A. Carbohydrates
• B. Proteins
• C. Lipids
• D. Fats

Hint:

Site-directed mutagenesis is a powerful technique for studying protein function by introducing specific mutations in the DNA sequence encoding the protein.

Answer 1

The Correct Option is B

Step 1: Understanding site-directed mutagenesis.
Site-directed mutagenesis is a method used to introduce specific mutations into a DNA sequence, allowing researchers to study the function of specific amino acids in proteins. This technique has facilitated extensive research in protein structure and function.
Step 2: Analyzing the options.
(1) Carbohydrates: Site-directed mutagenesis is not typically used for studying carbohydrates, as it is more suited to altering DNA that encodes proteins.
(2) Proteins: Correct — Site-directed mutagenesis is most commonly used to study proteins by altering specific amino acids and analyzing their effect on protein function.
(3) Lipids: Site-directed mutagenesis is not typically applied to lipids, as they do not have a DNA sequence to be altered.
(4) Fats: Like lipids, fats are not targeted by site-directed mutagenesis, which focuses on DNA and protein research.
Step 3: Conclusion.
The correct answer is (2) Proteins, as site-directed mutagenesis is used to study proteins by introducing specific mutations in their encoding genes.

Answer 2

Site-directed mutagenesis changes a specific codon within a cloned gene, and the whole point of doing so is to observe how that change affects the molecule the gene encodes. Checking each option against that logic:

1. Carbohydrates: Carbohydrate structures are built by enzymes acting on sugar substrates and are not directly encoded by a gene sequence in the way a protein's amino acid sequence is, so mutating a gene does not let researchers directly probe carbohydrate structure-function relationships the same way.
2. Proteins: Because the gene's codon sequence directly specifies the protein's amino acid sequence, changing one codon through site-directed mutagenesis changes exactly one amino acid in the resulting protein, letting researchers pinpoint the functional role of that single residue -- this direct gene-to-protein correspondence is exactly what makes the technique so powerful for studying proteins.
3. Lipids: Lipid molecules are assembled and modified by metabolic enzymes rather than being directly gene-encoded themselves, so mutating a gene sequence does not translate into a controlled change in a lipid molecule.
4. Fats: Like lipids generally, fats are synthesized through metabolic pathways rather than encoded directly by a gene sequence, so they are not the direct target of this gene-editing technique either.

Only proteins have a direct, codon-by-codon correspondence with the underlying gene sequence, which is what allows site-directed mutagenesis to probe their structure and function so precisely.

Therefore, the correct answer is proteins.