Left-right bias in pelvic vestiges can be used to infer involvement of which gene?

• A. Pitx2
• B. Pitx1
• C. Pax6
• D. Shh

Answer: (B)

Left-right bias in pelvic vestiges points to a gene that patterns hindlimb identity in the pelvic region. Pitx1 is the hindlimb/pelvic identity regulator, so changes in its activity or expression can cause one side to retain a vestige more than the other. This is seen in evo-devo studies where Pitx1 controls pelvic structures, and alterations in its expression explain why pelvic vestiges might show side-specific patterns. Pitx2 mainly handles left-right patterning of organs, not hindlimb identity, while Pax6 and Shh have different primary roles (eye development and broader limb patterning, respectively). Thus Pitx1 best explains the left-right bias in pelvic vestiges.