Which of the following best illustrates "FEEDBACK" in development ?
- As tissue (X) develops, it secretes something that induces tissue (Y) to develop
- As tissue (X) develops, it secretes something that slows down the growth of tissue (Y)
- Tissue (X) secretes RNA which changes the development of tissue (Y)
- As tissue (X) develops, it secretes enzymes that inhibit the development of tissue (Y)
Answer
(1) As tissue (X) develops, it secretes something that induces tissue (Y) to develop
Solution
In development, the growth of one tissue is linked to that of another through chemical signals.
As tissue (X) develops, it releases a chemical signal that induces the neighbouring tissue (Y) to develop; the development of (Y) is thus directly coupled to the progress of (X).
Such interaction, in which the output of one developing tissue regulates and drives the development of another, illustrates feedback in development.
Options (2), (3) and (4) describe only a change or inhibition of tissue (Y), not the inductive signalling by which one developing tissue directs the development of another.
Answer: (1)