What are the regulatory mutations responsible for the adapti

What are the regulatory mutation(s) responsible for the adaptive evolution of pelvic reduction in stickleback fish? (A) VISTA/mLAGAN (http://genome.lbl.gov/vista/) alignment of Pitx1 candidate region from pelvic-complete stickleback (SALR), . Red peaks indicate >40% sequence identity in 20-bp sliding windows; grey bars at top indicate repetitive sequences; and circles indicate microsatellite markers used in association mapping in fig. S1. (B) Reporter gene expression in transgenic animals. (C) Pel-2.5-kb^SALR from a marine population drives tissue-specific EGFP (green) expression in the developing pelvic bud of stage-32 larvae (36). (F) Detail of (C). (D and G) Altered Pel-Delta 2.5-kb^PAXB sequence from pelvic-reduced PAXB stickleback fails to drive pelvic EGFP expression. (E and H) A smaller fragment from marine fish, Pel-501-bp^SALR, also drives EGFP expression in the developing pelvic bud of multiple stage-30 larvae. This region is completely missing in PAXB.

Solution

Mutation refers to a \"change\" and regulatory mutation(s) are the change in DNA or RNA which ultimately changes the expression of other genes by a cell.

Regulatory mutations in stickleback fish:-  

Three-spine stickleback fish(Gasterosteus aculeatus ) undergo regulatory mutation and adapt evolution of pelvic reduction by deleting a tissue-specific enhancer of the Pituitary homeobox trancription factor1(Pitx1)gene-( a gene expressed in hind limbs and not in forelimbs and required for normal hindlimb development ).The regulatory mutation in these fishes are influenced by the inherent structural features of the Pitx1 locus. cis- regulatory mutations at the Pitx1 locus has been proposed as the basis of pelvic reduction. Many factors such as absence of gape- limited predatory fish,limited calcium availability and predation by grasping insects contribute to repeated evolution of pelvic reduction in sticklebacks fish.Although Pitx1 represents to be a strong gene for pelvic reduction, other genes in larger chromosome region may be the real cause of pelvic loss leading to secondary or trans-acting reduction of Pitx1 expression.Pelvic reduction in sticklebacks maps to a type of DNA lesion which may produce large regulatory changes in a single mutational leap( deletions that completely remove a regulatory enhancer).