"There are many families of zinc-finger proteins involved in DNA transcription, all very rapidly evolving," says Dernburg. "Gene duplication is common throughout the genome in all species, but unless a duplicated gene quickly acquires a new function, it is not likely to be conserved. The group of related zinc-finger protein genes in C. elegans offers an opportunity to address the question of how and why new zinc-finger proteins acquire new functions."
A model of reproduction
C. elegans is a tiny worm, typically a millimeter in length, admirably suited to the study of meiosis because it is completely transparent and reproduces very efficiently, producing over 200 progeny within a few days. Most C. elegans are hermaphrodites, which have two X chromosomes (XX), while some individuals are males with a single X chromosome (X0). The reproductive organs contain about half of the cells in an adult worm, and the process of meiosis can be observed at every stage, as chromosomes first come together during the pairing process, then later separate during meiotic division.
One result of failed pairing of X chromosomes is a high incidence of males having only one X chromosome. The observation that a mutant him 8 gene gives rise to a high incidence of males is what gave the gene its name.
"In all organisms, sex chromosomes do special things," says Dernburg. "For example, in species where an X and Y chromosome make a male, only very small regions of these chromosomes require control for successful pairing. So even though we saw there were nearby genes similar to him-8" -- which acts only on the C. elegans
Contact: Paul Preuss
DOE/Lawrence Berkeley National Laboratory