Pitx1's involvement in hind limb development is described in which vertebrate mentioned?

• A. Mouse
• B. Chicken
• C. Zebrafish
• D. Frog

Answer: (A)

Pitx1 is a transcription factor that helps specify hindlimb identity during vertebrate limb development. In mouse embryos, Pitx1 is expressed in the hindlimb bud and is necessary for proper hindlimb formation; when Pitx1 function is disrupted, hindlimb development is altered and can shift toward forelimb-like characteristics, illustrating its role in directing hindlimb identity. Among the vertebrates listed, the strongest, most clearly described evidence for this involvement appears in mouse models, which is why the described connection points to the mouse. While Pitx1-related limb patterning occurs in other species as well, the material in question emphasizes the mouse findings.