# DBT JRF 2022 — Question 87

Exam: DBT JRF 2022 · Section: B · Topic: Plant Biology › Rubisco & Chloroplast Genetics · Difficulty: Medium

## Question

Given below are two statements: Statement I: Large subunit of rubisco is encoded by chloroplast genome while small subunit of Rubisco is encoded by nuclear genome Statement II: Small subunit of rubisco has a transit peptide, which is cleaved off at the time of its translocation into plastids. Choose the correct answer from the options given below:

## Options

- **A.** Both Statement I and Statement II are true
- **B.** Both Statement I and Statement II are false
- **C.** Statement I is true but Statement II is false
- **D.** Statement I is false but Statement II is true

## Answer

Option A

## Explanation

Rubisco subunit encoding — nuclear vs. chloroplast genome: Rubisco (Ribulose-1,5-bisphosphate Carboxylase/Oxygenase) is the key enzyme in carbon fixation (Calvin cycle): Subunit composition of form I Rubisco (plants, most organisms): • L (Large) subunit: CHLOROPLAST-encoded (rbcL gene in the plastid genome). - ~55 kDa; contains the active site for CO₂ fixation. • S (Small) subunit: NUCLEAR-encoded (rbcS genes). - ~15 kDa; translated in cytosol with a transit peptide for import into the chloroplast stroma. - Transit peptide is cleaved upon import. - Assembly: (L2S2)₄ → hexadecameric complex (L8S8) This split encoding is an important example of the coordination between nuclear and plastid genomes. Answer: Rubisco large subunit (rbcL) = chloroplast genome; small subunit (rbcS) = nuclear genome (with transit peptide for chloroplast import).

Source: https://mypyqbuddy.com/questions/given-below-are-two-statements-statement-i-large-6a104cd5920734408bc0c766