Q.93 MATCH the signaling pathways in Group I with their functions in Group II, during the process of
development
Group I
P. Hedgehog signaling
Q. Hox proteins
R. Wnt signaling
S. Notch signaling
Group II
(i) Involved in signaling at 4-cell embryo stage in C. elegans through 𝑔𝑙𝑝1 expression
(ii) Involves frizzled receptor on target cell membrane and establish polarity in insects
(iii) Plays critical role in facial morphogenesis in vertebrates and its mutation causes cyclopia
(iv) Required for 𝑇 − 𝑏𝑥 transcription factor expression for vertebrate limb development
(A) P-iii; Q-ii; R-iv; S-i
(B) P-iii; Q-iv; R-ii; S-i
(C) P-iv; Q-iii; R-ii; S-i
(D) P-iii; Q-iv; R-i; S-ii

Developmental biology relies on key signaling pathways like Hedgehog, Wnt, Notch, and transcription factors such as Hox proteins to regulate processes from cell polarity to organ formation. This article breaks down a matching question on their specific roles, identifies the correct option, and explains all choices for exam preparation in molecular biology and genetics.

Correct Answer

The correct matching is (B) P-iii; Q-iv; R-ii; S-i. Hedgehog signaling (P) drives facial morphogenesis in vertebrates, with mutations causing cyclopia; Hox proteins (Q) control T-bx expression for limb development; Wnt signaling (R) uses frizzled receptors for insect polarity; Notch signaling (S) operates via glp-1 at the 4-cell stage in C. elegans.​

Hedgehog Signaling (P)

Hedgehog, particularly Sonic Hedgehog (Shh), patterns the ventral midline of the neural tube and facial structures in vertebrates. Mutations disrupt midline signaling, leading to holoprosencephaly like cyclopia (iii). It does not primarily handle limb digit identity via T-bx or early embryo signaling.​

Hox Proteins (Q)

Hox proteins act as transcription factors specifying anterior-posterior body axes and limb patterns in vertebrates. They regulate Tbx genes (like Tbx5 or Tbx4) essential for forelimb/hindlimb identity (iv). Unlike signaling ligands, Hox proteins function downstream in transcriptional control, not polarity or embryo signaling.​

Wnt Signaling (R)

Wnt signaling binds Frizzled receptors on target cells, activating β-catenin to establish planar cell polarity (PCP) in insects like Drosophila wing discs (ii). This differs from its roles in vertebrate axis formation or Notch-mediated decisions.​

Notch Signaling (S)

Notch signaling via GLP-1 receptor promotes pharyngeal muscle fate over body muscle at the 4-cell stage in C. elegans, regulating cell-cell interactions (i). It involves lateral inhibition, distinct from vertebrate facial or limb roles.​

Option Analysis

Option (B) uniquely aligns all functions: P-iii (cyclopia via Shh loss), Q-iv (Hox-Tbx in limbs), R-ii (Frizzled polarity), S-i (GLP-1 in C. elegans).​