The loss of ventral spines by modern freshwater sticklebacks is due to natural selection operating on the phenotypic effects of Pitx1 gene ________.
A) duplication (gain in number)
B) elimination (loss)
C) mutation (change)
D) silencing (loss of expression)

Question

Quizplus · Accepted Answer

Silencing of the Pitx1 gene expression is the reason behind the loss of ventral spines in modern freshwater sticklebacks. This has been identified through experimental studies where the introduction of Pitx1 gene from marine sticklebacks, which have ventral spines, to freshwater sticklebacks resulted in the development of ventral spines. Thus, it is clear that natural selection operates on the phenotypic effects of the silenced Pitx1 gene expression to reduce the development of ventral spines in freshwater sticklebacks.

The Loss of Ventral Spines by Modern Freshwater Sticklebacks Is