New research provides the best evidence yet that a fertilized egg's nucleus isn't the sole site of control for an embryo's development. Signals emanating from the cell's mitochondria—its power-generating organelles—also appear to influence how an organism grows.
Mitochondria carry their own DNA, which is unrelated to the genetic material in a cell's nucleus. Scientists have been unsure whether mitochondrial DNA has an impact on developmental processes.
To investigate this, Zuo-Yan Zhu and his colleagues at the Chinese Academy of Sciences in Wuhan cloned carp through a technique called nuclear transfer. This method removes the nucleus from one cell and inserts it into an egg that has had its own nucleus removed. However, instead of inserting carp nuclei into carp eggs, Zhu's team inserted them into goldfish eggs.