A new study on the sex life of molds is raising startling new questions about gene silencing, speciation and perhaps some facets of human reproduction.

The study, featured in the journal Cell, focuses on the mating habits of Neurospora crassa, commonly called pink bread mold - a fungus that has been a useful genetic model organism for more than half a century. Neurospora became famous when George Beadle and Edward Tatum used it at Stanford in 1941 for the first experiments in biochemical genetics - an achievement that won them the Nobel Prize.

"Fungus is very easy to manipulate," said Patrick K. T. Shiu, a postdoctoral fellow in the Stanford Department of Biological Sciences and lead author of the Cell paper. "It only takes two weeks for a genetic cross to mature, and you can insert or delete any gene you want."

When it comes to sex, molds and humans share at least one fundamental principle: In both species, the parents must donate a copy of their DNA to the offspring in order to successfully reproduce.

In most human cells, DNA resides in 23 pairs of chromosomes. One chromosome is inherited from the father, one from the mother.

Neurospora, on the other hand, contains only seven different chromosomes, and - during most of its life cycle - only one copy of each. During the sexual phase, one set from each parent briefly forms a cell with 14 chromosomes, each chromosome containing a grab bag of genetic information from one parent or the other. The corresponding chromosomes from each parent pair up and then separate to form progeny, which again have only seven chromosomes.

Silence of the genes

This complex cellular process - in which parental chromosomes pair up and split apart to form offspring or sex cells (sperm and eggs) - is called meiosis and occurs in all organisms that reproduce sexually, from people to plants to fungi.

In their recent Cell study, Shiu and his colleagues took a closer look at
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Contact: Mark Shwartz
650-723-9296
Stanford University
8-Feb-2002