Imagine that a very unusual animal species had the ability to make its own aromatic amino acids using a 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase enzyme similar to that of plants. What would happen if this animal foraged in a field of glyphosate-resistant plants?

Question

A.  No effect.
B.  They would become sick from the glyphosate that was sprayed on the plants.
C.  They would also become glyphosate-resistant.
D.  They would no longer need to make their own aromatic amino acids.

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?
 
Gather Content
· What do you already know about herbicide resistance transgenes?

  Consider Possibilities · Consider the different answer options. Which can you rule out?

Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

B.  They would become sick from the glyphosate that was sprayed on the plants.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses herbicide-resistance transgenes.
· What type of thinking is required?
        o This question is asking you to take what you already know and apply it to this unfamiliar situation.
· What key words does the question contain and what do they mean?
        o EPSP synthase is an enzyme normally only in plants that allows them to synthesize aromatic amino acids.
        o Glyphosate is an herbicide that kills plants by blocking EPSP.
        o Glyphosate-resistant plants are resistant because they have multiple copies of the EPSP gene.
 
Gather Content
· What do you already know about herbicide resistance transgenes?
        o Glyphosate is a powerful, biodegradable herbicide that kills most actively growing plants.
        o It works by inhibiting an enzyme called 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase, which plants require to make aromatic amino acids.
        o Animals do not make aromatic amino acids, so animals living in and around crops, or in waterways receiving crop run off, are unaffected by glyphosate.
        o To make glyphosate-resistant plants, scientists used a Ti plasmid to insert extra copies of the EPSP synthase gene into plants so they produce 20 times the normal level of EPSP synthase, enabling them to grow despite glyphosate’s inhibition.

  Consider Possibilities · Consider the different answer options. Which can you rule out?
        o Would the animal have no effect from eating in the glyphosate-resistant field? Most animals do not... but then animals normally do not have the EPSP gene.
        o Would the animals also become glyphosate-resistant? No, that could only happen if they acquired the transgene in multiple copies – very unlikely to happen.
        o Would the animals no longer need to make their own aromatic amino acids? Not likely.
 
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Would the animals become very sick from the glyphosate that was sprayed on the plants? Yes, very likely. If they had the plant enzyme, they would be affected just like the plants. Remember that glyphosate is sprayed in the field to kill weeds, so the trangenic plants are not affected but weeds are killed.

Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked what would happen to an animal with EPSP if it ate out of a field of glyphosate-resistant plants.
        o The question required you to take what you already know and apply it to this unfamiliar situation.
        o Did you recognize that the animal could not acquire glyphosate-resistance?
        o Did you realize that the glyphosate would block the animals’ EPSP enzymes?