35. The names of some genes in Column X and their involvement in photosystem I (PSI) or photosystem II (PS II) is provided in Column Y.
    
    Column X Column Y
    A   psb A                              i.   PS II
    B   psa A                              ii.  PS I
    C   lhcb 1
    D   lhca 1

Which one of the following combinations represents correct matches between columns X and Y?

(1) A-i, B-ii, C-i, D-ii                     (2) A-ii, B-i, C-ii, D-i
(3) A-i, B-ii, C-ii, D-i                           (4) A-ii, B-ii, C-i, D-ii

The correct answer is (1) A-i, B-ii, C-i, D-ii.

• A. psbA → PSII

  • Correct. The psbA gene codes for the D1 core reaction center protein specific to Photosystem II. D1 is central for charge separation and water splitting in PSII.​

• B. psaA → PSI

  • Correct. The psaA gene encodes a major core protein of Photosystem I, interacting directly with P700 and other PSI core subunits.​

• C. lhcb1 → PSII

  • Correct. lhcb1 encodes one of the main light-harvesting chlorophyll a/b-binding proteins (LHCII), which is the primary antenna complex for Photosystem II, found predominantly in grana.​

• D. lhca1 → PSI

  • Correct. lhca1 encodes a chlorophyll a/b-binding protein that is part of the LHCI complex, the major light-harvesting antenna of PSI localized mainly in stroma thylakoids.​

Photosystem Gene Assignments: PSII and PSI

Introduction

Key phrase: PSII PSI gene function psbA psaA lhcb1 lhca1

Photosystem I and II are highly specialized membrane complexes, each requiring unique protein subunits encoded by distinct genes for their structure and light-harvesting functions.​

Explanation of Each Match and Option

• A-i (psbA codes for D1 protein in PSII).​

• B-ii (psaA codes for core PSI protein PsaA).​

• C-i (lhcb1 codes for LHCII – the major PSII antenna protein).​

• D-ii (lhca1 codes for LHCI – a PSI antenna protein).​

Option 1 matches all the gene-protein relationships to the correct photosystem.

Key Facts: Gene-Protein Coordination in Photosystems