These are not homework questions. I saw these and some other questions mentioned as discussion in a document. I could find answer to others. I need just 3 or 4 sentences simple answers to these so that I can get a head-start. 1. Compare at least two different examples where concentration gradients are used during neurogenesis. Are the following examples OK? 1) AP and DV concentration gradients in insects form body axes, which specify proneural cluster. 2) In vertebrates, regional D-V concentration gradients specify the organization of the neural tube. 2. Compare and contrast at least two different functions for the same molecule in different contexts e.g., different stages of neurogenesis, different organisms, or cellular identity I was thinking of giving examples of insects (such as drosophila) and vertebrates as organisms. But I do not know which same molecule functions differently in these. Can examples of BMP or EGF molecules be given? 3. Compare and contrast examples of an extrinsic mechanism with an intrinsic mechanism of axonal growth. 4. Give at least three examples of different types of guidance cues that axons use to navigate to their target. How do they work? I know that attractant and repellent (such as semaphorin/plexin) are different types of guidance cues. But I do not understand in any detail to answer this question.