41. Which one of the following is a group of signalling molecules that act as morphogens during development of an organism and its effects are mediated through the receptor Patched and its binding partner Smoothened?
    (1) Hedgehog protein (2) Notch protein
    (3) Wnt protein (4) β-catenin

The signaling molecule group that acts as morphogens during development, exerting their effects through the Patched and Smoothened receptors, is:

(1) Hedgehog protein

Explanation:

• The Hedgehog (Hh) family of proteins, including Sonic Hedgehog (Shh), Indian Hedgehog (Ihh), and Desert Hedgehog (Dhh), are key morphogens that play vital roles in signaling pathways during embryonic development. They control cell proliferation, differentiation, and tissue patterning by forming gradients that influence cell fate decisions.

• Hedgehog proteins bind to the Patched receptor, relieving its inhibition of the Smoothened transducer, which then propagates intracellular signals to modulate gene expression accordingly.

• These pathways are highly conserved and pivotal for organogenesis, including limb formation, neural patterning, and organ development.

• Dysregulation of Hedgehog signaling is linked to developmental disorders and cancers, making it a significant focus of biomedical research.

Summary:

Hedgehog proteins are vital morphogens that influence embryonic development and tissue homeostasis through their interaction with the Patched and Smoothened receptor complex, orchestrating complex developmental processes in multicellular organisms.

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This content provides an overview of the crucial role of Hedgehog family proteins as morphogens in developmental biology, emphasizing their mechanisms of action and significance in health and disease.