A-Animals are not affected by Bt toxin in plant crops because 1. animals have th

Question

A-Animals are not affected by Bt toxin in plant crops because
1. animals have the enzymes to convert it to a nontoxic substance.
2. animals do not produce aromatic amino acids so Bt toxin can not be incorporated into metabolic pathways.
3. while it is toxic to insects, it is a normal metabolite for animals
4. animals lack the enzymes to interact with it.
5. it is destroyed by acids in the stomach.

B-Gene therapies can have deleterious side effects because
1. when foreign DNA is introduced into cellular nuclear DNA it can affect other DNA/protein's expression, and in some circumstances, lead to cancers.
2. cells will hijack this foreign DNA and use it to overthrow all safeguards to become an alien 6 foot virus.
3. the foreign DNA can mutate and replace all normal DNA.
4. extra body parts can result from overexpression of recombinant DNA.

C-Which of the following is an example of reverse genetics?
1. identifying a protein-protein interaction by a yeast two-hybrid screen
2. finding a mouse gene can direct eye formation in Drosophila
3. isolating clones from a library using hybridization of a radiolabeled probe
4. mutating a cloned gene and substituting the mutant copy for the wild-type copy in an organism to assess its function
5. observing a phenotype and isolating the gene that produces that phenotype

Explanation / Answer

A) The important thing is to recognize that Bt toxin is a protein. In insects, the partial cleavage of this protein in the gut results in an activated form of the toxin. In the stomachs of animals, the high acid content fully breaks down the protein into its constituent amino acids. Since the protein is fully digested, it has no activity. Thus, answer 5 is correct.

B) Answers 2, 3, and 4 all have impossible parts (6 foot virus, replace all DNA, and extra body parts). By process of elimination, this leaves answer 1, which is also the only true answer. Inserting DNA can have consequences for genes adjacent to the inserted material as well as genes far away on the same chromosome.

C) Think of forward genetics as going from phenotype to genotype: By analyzing the genes of different known phenotypes, you can discover which genes cause that phenotype. Reverse genetics is just the opposite. Having known sequences of DNA, you can alter the gene to analyze the phenotypes that result. Therefore, answer 4 is correct.

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