67. Most of DNA binding protein binds to DNA by particular motif to modulate gene expression. Genes which are under regulation of gibberllin acid have GRE which is recognized by transcription factor GREB. The motif in GREB is
    (1) Leucine Zipper            (2) bZIP

(3) Zinc finger                  (4) Homeodomain

Correct answer: (3) Zinc finger

Explanation:

• DNA-binding proteins that regulate gene expression typically contain specific DNA-binding motifs.

• GREB, a transcription factor recognizing the gibberellin response element (GRE), has a zinc finger motif. Zinc finger domains stabilize the protein-DNA interaction and enable sequence-specific binding to DNA.

• Other common DNA-binding motifs include leucine zipper and bZIP (basic leucine zipper), which function similarly but are not known for GREB. The homeodomain motif is common in developmental regulators but not GREB.

• Zinc finger proteins are widespread and versatile transcription factors with a well-characterized role in hormone-responsive gene regulation, including gibberellin signaling.

Option-wise:

• (1) Leucine zipper — typical of bZIP proteins, but not GREB.

• (2) bZIP — basic leucine zipper, different class.

• (3) Zinc finger — correct motif of GREB.

• (4) Homeodomain — typical in developmental TFs, not GREB.