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Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892

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BuyFindarrow_forward

Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892
Textbook Problem

In the embryonic development of the eye:

a. the optic vesicle cells permanently adhere to each other to prevent movement, whereas the optic cup cells are very motile.

b. the optic cup induces the surface ectoderm to form the lens placode.

c. gradients determine that the ectoderm overlying the lens vesicle develops into the optic vesicle.

d. microtubules powered by myosins and microfilaments powered by dyneins move the eye components around in the head region.

e. cadherins function in the presence of calcium to allow the lens placode and optic cup to break apart.

Summary Introduction

Introduction:

The development of the eye is a part of organogenesis. The optic vesicles develop into the eyes. These vesicles are derived from the neural ectoderm’s specific region. The development is controlled by the expression of Pax6, Rx1, and Six3 factors. These are transcription factors expressed in the most anterior tip of the neural plate.

Explanation

Justification/explanation for the correct answer:

Option (b) states that the optic cup induces the surface ectoderm to form the lens placode. The double walled optic cup is formed when the outer wall of vesicles thickens, flattens at the region of contact, followed by inward pushing. These optic cups are responsible for inducing the surface ectoderm into thickening into a disc-like swelling, which is termed as lens placode. These form the lens vesicles. Hence, option (b) is correct.

Explanation for the incorrect answers:

Option (a) states that the optic vesicle cells permanently adhere to each other to their prevent movement, whereas the optic cup cells are very motile. The optic vesicles make contact with surface ectoderm and do not permanently adhere to each other. The optic cup cells are less motile. So, it is an incorrect option.

Option (c) states that gradients determine that the ectoderm overlying the lens vesicle develops into the optic vesicle...

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