Many insects, like moths and flies, undergo complete metamorphosis. What would you predict about gene expression in these two kinds of insects?

Question

A.  The basic organization of homeotic genes is the same in both larvae and adult, but the expression of some other genes must be different.
B.  Completely different sets of genes must be used in the development of larvae and the adult.
C.  The order of homeotic genes along the body axis must be different in larvae and adult.
D.  The same genes are expressed at each stage, but the age and number of cells accounts for the minor morphological differences.

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 homeotic genes and metamorphosis?

  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

A.  The basic organization of homeotic genes is the same in both larvae and adult, but the expression of some other genes must be different.

Clarify Question
· What is the key concept addressed by the question?
        o This question addresses homeotic genes and metamorphosis.
· What type of thinking is required?
        o This question is asking you to weigh and judge, or evaluate, evidence to choose the best of the possible answers.
· What key words does the question contain and what do they mean?
        o Complete metamorphosis refers to the development of insects like flies, moths, and butterflies, where the larva transforms into a completely different looking adult form.

  Gather Content
· What do you already know about homeotic genes and metamorphosis?
        o In our text, we saw a diagram illustrating how the expression of homeotic genes from head to tail is very similar in both the larva and adult fly.
        o Even in mice, the basic pattern of expression is similar.
        o Nevertheless, the morphology of the larva and adult fly are very different.

  Consider Possibilities · Consider the different answer options. Which can you rule out?
        o Would you predict that completely different sets of genes must be used in the development of larvae and the adult? No, we know that isn’t true. For instance, we know the homeotic genes are used in both.
        o Would you predict that the order of homeotic genes along the body axis must be different in larvae and adult? No, we know that isn’t true. The homeotic genes are expressed in the same basic pattern in both.
        o Would you predict that the same genes are expressed at each stage, but the age and number of cells accounts for the minor morphological differences? No, there must be some gene expression differences to account for the BIG morphological differences.

  Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
        o Would you predict that the basic organization of homeotic genes is the same in both larvae and adult, but the expression of some other genes must be different? Yes, this is the most reasonable prediction.

  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 you would predict about gene expression in metamorphic insects.
        o The question required you to weigh and judge, or evaluate, evidence to choose the best of the possible answers.
        o Did you recognize that the larva and adult of an insect with complete metamorphosis look very different?
        o Did you remember that the homeotic genes are expressed in the same basic order in both the larva and the adult?