Worms from the heights of space and the depths of the earth were in the news last week, one well-known species soaring to the heavens as part of a space flight experiment and a previously undiscovered species revealing the surprising extent of multicellular life in the hidden depths of earth.
The Worm from the Heavens Caenorhabditis elegans perhaps qualifies as the most well-known of all worms. This 1mm roundworm, is a staple model organism in molecular biology. It’s easy to grow and store, possesses a simple neuronal network, and is transparent, making it easy to study cell differentiation and development. It was the first multicellular organism to have its genome sequenced, and the developmental fate of all its somatic cells has been studied. In some ways we know C. elegans better than we know ourselves. Continue reading “Worms from Heaven and Hell”
How do you explain the phenomenon of incomplete penetrance, which happens when individuals carrying an allele for a given phenotype don’t always express the phenotype? For instance, individuals carrying the same mutation associated with a genetic disease do not always develop that disease.
Sometimes environment influences gene expression and plays a role, or other genetic differences among the individuals of a population can affect the expression of the gene in question. But, incomplete penetrance is also observed in model organisms that are raised in controlled environmental conditions and that have “identical” genetic makeup.
Biologists have proposed that random variability in gene expression could account for such events, and in clonal populations of microorganisms random variation in gene expression may even be important for generating genetic variability. However, in more complex organisms that have specific cell types organized into tissues and organs, gene expression needs to be highly controlled for the organism to develop properly. So, if there are random fluctuations in gene expression, somehow they need to be “buffered” in normal development.