Question

chapter 17 section 5

5. Complex development Aa Aa E Every somatic cell in an animal embryo has a complete set of genes that code for the structure of the entire animal. As the embryo develops, certain genes get turned on in certain areas of the embryo to develop limbs, eyes, and so forth. In order for the animal to develop properly, these genes need to be turned on and off in a precise order. Many signals and hormones in the tissue of the embryo regulate how this organization happens Sometimes, when one tissue starts to develop, it releases molecular signals called influence the development of another type of tissue nearby. This is called embryonmorphogens ntal biologists describe this by saying that the first tissue, Tissue A, induces the second macrophages to trigger or homeotic genes How do biologists determine which tissue induces another tissue? Consider the hypothesis that Tissue A induces the formation of Tissue B. You can test this in one of three ways: 1. Observe when and where Tissue B appears relative to Tissue A 2. Remove Tissue A and observe the effects. 3. Transplant Tissue A into a new site where it is normally not found and observe the effects. If Tissue A does induce the formation of Tissue B, which of the following would you predict to be the result of the second experiment just described? O Removal of Tissue A would causes an excess formation of Tissue B. O Removal of Tissue A would not affect the formation of Tissue B. O Removal of Tissue A would prevent the formation of Tissue B

Answer 1

Q1. Morphogens

Reason : morphogens are the signalling molecules that trigger of that influence development.

Q2. Option 3 i.e removal of tissue A would prevent formation of tissue B

Reason : if tissue A is inducing tissue B then obviously it is always mandate for tissue A to be present to give signals to for formation of B.

3. induces, dorsal lip when transplanted into the non pigmented ventral region it formed the dorsal structures , so it is induces.