All this information does not completely explain Cullis's assertion that the environment can in a single generation help sift out the useful mutations.
This is where polymerase chain reaction (PCR) amplification of DNA comes in. Through this process, the researchers could see when a specific DNA sequence (in this case LIS-1) appears or disappears.
When the plastic strand is grown under low nutrient conditions, the LIS-1 sequence, which had been absent, appears and continues for future generations. Since the LIS-1 sequence helps plants survive when there is a shortage of nutrients, its presence helps confirm Cullis's belief that the environment can act on how a plant mutates and keep helpful mutations, even within one generation.
These findings help explain why the top of a redwood is genetically different from the bottom. Young redwoods grow by the tips of the existing branches budding into meristems. Each new meristem is different from the tree because the environment has affected its genetic makeup. And as the redwood grows, the top becomes more and more genetically different from the bottom.
Due to the controversy surrounding Cullis's findings, many scientists are hesitant to accept them as true. Cullis himself recalls at first being skeptical and thinking, "If this really works [we can] get a plant that's better adapted to its environment in one generation."
These adapted plants have practical uses. Cullis hopes to identify the specific gene sequence responsible for flax's ability to withstand harsh environments and insert it into the DNA sequence of other plants so that they too can withstand trying environments.
|Contact: Kevin Mayhood|
Case Western Reserve University