Animal geneticists owe their success to mice and the fruit fly Drosophila; microbial geneticists are indebted to the bacterium E. coli. Now molecular biologists propose that a small weed will prove to be a similar boon to plant geneticists.
Plant genetics has lagged behind other fields in the recent rapid progress in understanding mechanisms of inheritance and in applying that knowledge to genetic engineering. The explanation often given for this lag is the amount and complexity of the genetic material, called the genome. Plants have large amounts of repetitive DNA -- sequences of unknown function present in thousands of copies and scattered throughout the chromosomes. In addition, plants often have extra copies of their entire set of chromosomes.
A plant in the mustard family may allow geneticists to work with a much simpler genome. This harmless weed, Arabidopsis thaliana, which grows to about 5 inches tall, contains about 1 percent the amount of DNA in wheat, and less than 0.5 percent the amount of repetitive sequence. In addition, it is well suited for research: Its life cycle is only five weeks; one plant can produce thousands of seeds; and dozens of plants can be grown in a 2-inch-diameter pot. More than 75 genetic mutations have already been described and assembled into a map of the plant's five chromosomes. …