| Gene Mutation
As the text mentions, genes mutate, change accidentally, and in mutating
may cause a plant to have new characteristics. These mutations are
important for the evolution of plants in natural environments, for
breeding improved crops, and for studying how genes control plant
metabolism and development. Some of the easiest mutations to study are
the ones that cause visible changes in the plants. At the web site
"Mutants of Maize" there are sets of descriptions and photographs corn,
also called 'maize,' mutants.
Study several of these and notice some of
the many ways that plant development can be altered. Some of the mutants
cause leaves to have white spots, so the mutation is probably preventing
the plant from synthesizing the green pigment chlorophyll. As you look
at photos of other mutants, can you guess what the mutated gene might be
doing (or not doing)? Causing mutations is easy for plant scientists,
understanding what the mutated genes do is the big problem.
|
|
|
| Characteristics of Life: Exploring the Solar
System
We are actively searching for life in the solar system, looking for 1)
living bacterium-like creatures, 2) traces that life existed in the past
on Mars and 3) evidence that life could still originate in the future on
one of the moons of Jupiter or Saturn. The "National Aeronautics and
Space Administration (NASA)" web site contains a great deal of
information on this topic.
The site is updated frequently, so you may
have to use your own ingenuity to find a site related to searching for
life, but once you arrive at the page entitled "Solar System
Exploration", scroll down until you find a list of topics. There should
be headings related to Pathfinder, Mars Global Surveyor, Galileo (which
is in orbit around Jupiter) or Cassini (on its way to Saturn and its
moon Titan, but it will not arrive there until about 2004). As you
examine these web sites, notice that we are searching for life in very
different types of places. Read the text in Box 1.1 in your text book,
and think about how the various characteristics of life must be used as
the basis for this exploration of the solar system.
|
