Correct option is D
Explanation-
Statement A - Lmx1b gene is expressed in dorsal mesenchyme - CORRECT
Lmx1b is crucial for dorsal limb identity. It is activated by Wnt7a, and its absence leads to ventralized limbs (e.g., footpads on both sides). Mutations in Lmx1b cause Nail-Patella syndrome in humans.
Statement B - Shh is expressed in the posterior region.
True, but Not related to the condition asked.
Shh is expressed in the Zone of Polarizing Activity (ZPA) in the posterior limb bud. It regulates anterior-posterior patterning, not dorsoventral. So, not relevant to Nail-Patella syndrome.
Statement C - Wnt7a gene is expressed in dorsal ectoderm - CORRECT
Wnt7a is a key dorsal ectodermal signal. It induces Lmx1b in the underlying mesenchyme. Wnt7a knockout mice have ventralized limbs — footpads on both sides. So, it's directly linked to dorsoventral patterning defects.
Statement D - Hoxa13 and Hoxd13 are expressed in the distal region.
True, butNot relevant to dorsoventral defects.
These genes pattern the proximal-distal axis, especially the digits and autopod. Their mutations cause limb truncations (e.g., synpolydactyly) but not dorsal-ventral identity problems.
Statement E - Tbx5 and FGF10 are expressed in the lateral plate mesoderm involved in formation of limb bud
True, but Not related to dorsoventral defects.
These genes are involved in limb bud initiation (Tbx5 for forelimb, FGF10 for outgrowth). Again, not connected to dorsoventral patterning or Nail-Patella syndrome.
Final Answer:
Option d – A and C only
