  May 05, 2013 The apical tip of fruitfly testis containing
germline stem cells and differentiating germ cells. Copies of Y
chromosome are marked with either red or blue. Using this
method, the authors discovered that germline stem cells inherit
specific copies of Y (and X) chromosomes. Credit: Yukiko
Yamashita  The human body contains trillions of cells, all
derived from a single cell, or zygote, made by the fusion of an
egg and a sperm. That single cell contains all the genetic
information needed to develop into a human, and passes identical
copies of that information to each new cell as it divides into
the many diverse types of cells that make up a complex organism
like a human being.  If each cell is genetically identical,
however, how does it grow to be a skin, blood, nerve, bone or
other type of cell? How do read the same but divide into very
different types?  Researchers at the University of Michigan have
found the first direct evidence that cells can distinguish
between seemingly identical copies of c