Question 1

What is the family of cell-adhesion molecules that require calcium to adhere to the same molecules on another cell?&#10;A) Cadherins&#10;B) CAMs&#10;C) Integrins&#10;D) Laminins

Accepted Answer

Cadherins are a class of type-1 transmembrane proteins that depend on calcium ions to function properly. They play a crucial role in cell-cell adhesion, ensuring that cells within tissues are bound together.

Question 2

Which of the following is not associated with the differential adhesion hypothesis?&#10;A) Cells sort according to differences in adhesiveness and surface tension&#10;B) Cells sort similarly to molecules of two immiscible liquids&#10;C) Cells sort according to the types and numbers of cell-adhesion molecules&#10;D) Cell sorting recapitulates the final positions of cell layers in the normal embryo.

Accepted Answer

The differential adhesion hypothesis primarily explains how cells sort based on differences in adhesiveness and surface tension, similar to molecules of two immiscible liquids, and according to the types and numbers of cell-adhesion molecules. It does not directly address the recapitulation of the final positions of cell layers in the normal embryo, which is more related to the outcomes of cell sorting rather than the mechanism itself described by the hypothesis.

Question 3

Which of these statements is true of cells moving through the primitive streak of a chick or a mouse embryo?&#10;A) Cells become mesenchymal in nature.&#10;B) Cells maintain their epithelial nature.&#10;C) Cells strengthen adherens junction complexes.&#10;D) Cells maintain their tightly packed organization.

Accepted Answer

Cells moving through the primitive streak undergo an epithelial-to-mesenchymal transition (EMT), where they lose their epithelial characteristics and gain a mesenchymal phenotype, allowing them to migrate individually.

Question 4

The first cleavage event in a C. elegans embryo gives rise to two differently sized cells with different content and fates. What is this type of cell division called?&#10;A) Asymmetric division&#10;B) Symmetric division&#10;C) Radial division&#10;D) Spiral division

Accepted Answer

Asymmetric division results in two daughter cells of different sizes and developmental potentials, as seen in the first cleavage of a C. elegans embryo.

Question 5

Which of the following does not play a role in the formation of a blastocoel?&#10;A) Sodium&#10;B) Osmosis&#10;C) Tight junctions&#10;D) Apoptosis

Accepted Answer

The blastocoel is formed during early embryonic development as a fluid-filled cavity. Sodium ions and osmosis play crucial roles in generating the osmotic pressure necessary for the accumulation of fluid, while tight junctions between cells ensure the integrity and containment of the blastocoel. Apoptosis, or programmed cell death, does not contribute to the formation of the blastocoel but is involved in other developmental processes such as differentiation and organogenesis.

Question 6

What is the subcellular event that provides the force required for puckering the epithelium during invagination?&#10;A) Inhibition of myosin motor activity&#10;B) Activation of Snail protein&#10;C) Endocytosis of cadherins&#10;D) Asymmetric actin-based contraction

Accepted Answer

Asymmetric actin-based contraction provides the force required for puckering the epithelium during invagination by generating mechanical tension that leads to the deformation of cell shape necessary for this process.

Question 7

Which of the following cell movements involves remodeling of intercellular junctions to guide medio-lateral intercalation?&#10;A) Delamination&#10;B) Involution&#10;C) Epiboly&#10;D) Convergent extension

Accepted Answer

Convergent extension involves the remodeling of intercellular junctions to guide medio-lateral intercalation, which is a process where cells rearrange themselves in a way that the tissue narrows (converges) and lengthens (extends). This is crucial for various morphogenetic processes, including gastrulation and neurulation.

Question 8

Which of the following embryonic cell movements involves the separation of cells from a continuous sheet of cells?&#10;A) Ingression&#10;B) Involution&#10;C) Epiboly&#10;D) Convergent extension

Accepted Answer

Ingression involves the movement of individual cells from a surface layer into the interior of the embryo, effectively separating them from a continuous sheet of cells. This process is crucial for the formation of different layers and structures within the developing embryo.

Question 9

What is the ectodermal interface between non-neural ectoderm and the neural plate during neurulation called?&#10;A) Neural fold&#10;B) Neural crest&#10;C) Neural furrow&#10;D) Neural groove

Accepted Answer

The neural fold is the ectodermal interface between the non-neural ectoderm and the neural plate during neurulation.

Question 10

Which of the following results from a failure to close the neural tube in the fore- and midbrain regions?&#10;A) Rachischisis&#10;B) Craniorachischisis&#10;C) Anencephaly&#10;D) Spina bifida

Accepted Answer

Anencephaly results from a failure to close the neural tube in the fore- and midbrain regions, leading to the absence of a major portion of the brain, skull, and scalp.

Deck 7: Morphogenesis: Change in Form in the Early Embryo