Summary of the imaginal disc story -

Having followed the discoveries of the team working on this problem, you have (hopefully!) deduced that allowing the rate of destruction of a morphogen to decrease over time can have the effect of ensuring that the tissue and its morphogen gradient grow in scale with one another.

The "French flag" (pattern of positional information based on a gradient) therefore remains as a French flag, with no extra stripes or missing parts, and nothing becoming disrproportional

Before going on to the next section, take a moment to ask yourself the following questions:

• Did you think of this solution as soon as you saw the problem (when reading the pdf?)
• If so, would you have still done the whole sequence of the experiments? Were there any that could be missed out?
• If you did not see the solution at once (most people do not, not even professional scientists), at what point did you see it? Why did you see it then?

(Considering questions such as those above is an example of 'reflective practice': the answers do not tell you any more scientific facts, but they can guide you in the process of becoming a scientist).

When you are ready to leave the world of imaginal discs, to consider a quite different type of problem, please click here.