Cover photograph (Copyright © 2008, American Society for Microbiology. All Rights Reserved.): A telomerase RNA mutation causes the Tetrahymena thermophila micronucleus to delay in mitotic anaphase. An antibody to phosphorylated histone H₃, stained red, binds to condensed chromatin during mitosis. This allows visualization of the cell's mitotically dividing micronucleus amongst the cell's amitotic macronucleus, stained in blue, which does not bind this antibody. The mitotic micronuclear spindle and cilia are stained green with an antibody to alpha-tubulin. The chromatin from this telomerase RNA mutant micronucleus appears joined from one spindle pole body to the other, unlike that in a wild-type micronucleus, which segregates into two daughter micronuclei. (See related article on page 1712.)