Question 1

Which of the following best describes the process of primary neurulation in vertebrate development?

Accepted Answer

The neural plate folds and converges at the dorsal midline, neural folds adhere, and the cells merge to form the neural tube.

Question 2

A deficiency in which nutrient is most commonly associated with increased risk of neural tube closure defects such as spina bifida?

Accepted Answer

Folic acid

Question 3

During neural tube closure, what molecular change allows the separation of neural and epidermal cells?

Accepted Answer

Switch from E-cadherin to N-cadherin expression in neural cells

Question 4

Which of the following is a consequence of failure to close the anterior neuropore during neural tube development?

Accepted Answer

Anencephalus

Question 5

Spina bifida aperta can present in several forms. Which form is characterized by the spinal cord and/or nerves not being covered by meninges or skin?

Accepted Answer

Myeloschisis

Question 6

Which signaling molecule is primarily responsible for inducing the formation of the floor plate in the ventral neural tube?

Accepted Answer

Sonic hedgehog (Shh)

Question 7

What is the main difference between primary and secondary neurulation?

Accepted Answer

Primary neurulation involves folding of the neural plate, while secondary neurulation involves cavitation of a solid chord.

Question 8

Which of the following gradients is crucial for establishing dorsal-ventral polarity and neuronal identity in the neural tube?

Accepted Answer

Gradient of Shh (ventral) and TGF-β/BMP (dorsal) proteins

Question 9

Experimental implantation of a second notochord adjacent to the neural tube results in which of the following outcomes?

Accepted Answer

Induction of a second floor plate and a second set of motoneurons

Question 10

During vertebrate eye development, which event is directly triggered by the contact of the optic vesicle with the epidermis?

Accepted Answer

Formation of the lens placode

Question 11

Which gene is inhibited in the center of the eye field to allow the formation of two optic vesicles?

Accepted Answer

Pax6

Question 12

Elevated expression of Sonic hedgehog (Shh) in the prechordal plate leads to which developmental abnormality in the eye?

Accepted Answer

Cyclopia (failure to split the eye field)

Question 13

Which cell type in the skin is derived from the neural crest and migrates into the epidermis?

Accepted Answer

Melanocyte

Question 14

Patterning of hair follicle placodes is directed by which two factors secreted by dermal cells?

Accepted Answer

Wnt10 and Dickkopf (Dkk)

Question 15

Which of the following is TRUE regarding the origin of the epidermis and dermis?

Accepted Answer

Epidermis is derived from ectoderm, while dermis is derived from mesoderm.

Question 16

Which region of the mesoderm forms the notochord, and what is its primary function during development?

Accepted Answer

Chordamesoderm; forms the primary axial skeleton and induces neural tube formation

Question 17

Which process is responsible for the periodic formation of somites along the anterior-posterior axis in vertebrate embryos?

Accepted Answer

Oscillatory expression of Notch signaling at the posterior boundary

Question 18

What is the fate of the ventromedial cells of a newly formed somite?

Accepted Answer

They undergo mitosis, lose epithelial characteristics, and become mesenchymal to form the sclerotome.

Question 19

Which equation best describes the osmotic gradient established by Na+/K+-ATPase activity that leads to water filling the brain ventricles?

Accepted Answer

$$\Delta \pi = RT (C_{in} - C_{out})$$

Lec 09 Dev Bio

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