Who, What, Where, When and Why? Science (scientia : to know)

Who, What, Where, When and Why?

Science (scientia : to know)

The Scientific Method: A model for problem solving that follows a well

defined procedure

Defining the ProblemWhat is causing limb mutations in Amphibians?

Collecting Information Amphibian skin is permeable to substances in

the water, air and land. Amphibians start their life in water and end up

land; they are exposed to many threats Increased UV radiation is getting through a

thinning ozone layer. Retinoic acid occurs in vertebrate embryos and

influences the development of limbs. Trematode cysts have been found clustered in

developing limb buds.

Hypotheses Increased UV radiation is damaging the genes

directing limb development (R. Mc Kinnell) Chemicals in the water, acting either singly or

together, are penetrating the frog’s skin causing mutations.

Abnormally high concentrations of retinoic acid and similar chemicals are affecting limb development at the tadpole stage. (J. Bantle)

Trematode cysts are splitting developing limb buds in multiple places. (S. Sessions)

Testing the Hypotheses Tissue samples are observed under the microscope.

Searching for damaged chromosomes. (Mc Kinnell) Tadpoles are incubated for 72 hours in a solution

containing an insecticide that was subjected to UV radiation. (Previous tests indicate that certain insecticides are transformed into retinoid like compounds in the presence of UV radiation.

J. Bantle) Plastic beads are surgically implanted into

developing limb buds. The beads mimic trematode cysts. The tadpoles are allowed to develop under normal conditions. (S. Sessions)

Conclusions No visible genetic damage was determined with

the technique used by Mc Kinnell. Other techniques will be applied to retest the hypothesis.

Bantle concluded that insecticides can be transformed into chemicals (when subjected to UV radiation) that can cause mutations like those observed.

Sessions showed that plastic beads inserted into developing limb buds can cause mirror image duplications. Actual cysts need to be implanted into developing limb buds and analyzed.