Question

What are the correct steps in the synthesis of light chain of immunoglobulins? A. mRNA, B. Rearranged DNA, C. Original DNA, D. Primary transcript, E. Protein (light chain of Ig) Choose the correct answer from the options given below:

• A. A, B, C, D, E \
• B. C, B, A, D, E \
• C. C, B, D, A, E \
• D. E, A, D, B, C

Hint:

Antibody expression is unique! DNA rearrangement (B) happens before transcription (D), breaking the normal rules of standard gene expression.

Answer 1

The Correct Option is C

Step 1: Concept Immunoglobin light chains are synthesized through a specialized gene expression pathway. Before transcription can even begin, the genome undergoes somatic recombination to assemble the functional antibody gene.

Step 2: Meaning The pathway flows from the initial germline genome configuration through somatic gene shuffling, transcription, RNA processing, and finally translation.

Step 3: Analysis Let us follow the chronological steps of this process: 1. The process starts with the germline configuration: the Original DNA (C). 2. Somatic recombination shuffles and joins specific variable (V) and joining (J) gene segments to construct Rearranged DNA (B). 3. This rearranged gene layout is transcribed to produce a long Primary transcript (D). 4. Splicing removes introns from the primary transcript to yield mature mRNA (A). 5. Finally, ribosomes translate the mature mRNA into the functional antibody light chain Protein (E).

Step 4: Conclusion The exact physical sequence of events is C $\rightarrow$ B $\rightarrow$ D $\rightarrow$ A $\rightarrow$ E. This aligns with option C. Final Answer: (C)