Test on Human Limb Development and Congenital Anomalies

Question 1: The Wnt pathway is responsible for determining the ventral and dorsal limb axis.

A. Ano

B. Ne

Explanation: The Wnt pathway, involving the transcription factor Lmx-1, is a signaling center that controls the ventral and dorsal limb axis.

Question 2: Which of the following conditions is directly associated with a deficiency in cartilage-derived morphogenetic protein during embryogenesis?

A. Increased interdigital necrosis

B. Grebes’ chondrodysplasia

C. Limb truncation

D. Holt-Oram syndrome

Explanation: The study materials state that "Deficiencies in cartilage-derived morphogenetic protein are associated with various forms of brachydactyly. Grebes’ and Hunter-Thompson chondrodysplasias are associated with severe brachydactyly and have been directly related to a deficiency of cartilage-derived morphogenetic protein."

Question 3: Transplantation of the Zone of Polarizing Activity (ZPA) causes mirror duplication of the radial aspect of the limb.

A. Ano

B. Ne

Explanation: The study materials state that transplantation of the ZPA or sonic hedgehog protein causes mirror duplication of the ulnar aspect of the limb, not the radial aspect.

Question 4: The Wnt signaling pathway, which is responsible for controlling spatial development, resides in the dorsal ectoderm.

A. Ano

B. Ne

Explanation: The study materials state that 'The Wnt signaling pathway resides in the dorsal ectoderm and controls this spatial development.'

Question 5: According to the study materials, what is the effect of transplantation of the sonic hedgehog protein on limb development?

A. It causes mirror duplication of the radial aspect of the limb.

B. It causes mirror duplication of the ulnar aspect of the limb.

C. It inhibits limb development entirely.

D. It leads to the complete absence of digits.

Explanation: The study materials state that 'Transplantation of the ZPA or sonic hedgehog protein causes mirror duplication of the ulnar aspect of the limb'.