Question 1

The apical ectodermal ridge runs in which direction in the developing limb bud?&#10;A) Antero-posterior&#10;B) Dorso-ventral&#10;C) Proximo-distal&#10;D) Left-right

Accepted Answer

B

Question 2

What is the correct flow of interactions that determines proper positioning and outgrowth of the forelimb?&#10;A) Lateral plate - Hox - Tbx5 - FGF-10 - apical ectodermal ridge&#10;B) Lateral plate - Tbx4 - Hox - FGF-10 - apical ectodermal ridge&#10;C) Lateral plate - Hox - Tbx4 - FGF-10 - apical ectodermal ridge-&#10;D) Lateral plate - Tbx5 - Hox - FGF-10 - apical ectodermal ridge

Accepted Answer

The correct sequence starts with the lateral plate mesoderm, which expresses specific Hox genes that help determine the anterior-posterior axis and type of limb (forelimb or hindlimb). Tbx5 is then expressed in the forelimb region, which is crucial for forelimb development. FGF-10 acts as a signaling molecule that promotes the outgrowth of the limb bud by interacting with the apical ectodermal ridge (AER), a critical structure for limb development.

Question 3

Which of the following refers to a chemical or infection that interferes with embryonic development, leading to defects in the animal?&#10;A) Teratogen&#10;B) Mutagen&#10;C) Morphogen&#10;D) Carcinogen

Accepted Answer

Teratogens are substances or factors that can cause congenital abnormalities or defects in the developing embryo or fetus. Examples include certain drugs, infections, and exposure to radiation.

Question 4

Which of the following intercellular signaling pathways directly controls the sequence of limb digits across the antero-posterior axis?&#10;A) FGF&#10;B) Shh&#10;C) Wnt&#10;D) BMP

Accepted Answer

Shh (Sonic hedgehog) signaling pathway directly controls the patterning of the limb digits across the antero-posterior axis.

Question 5

Which of the following intercellular signaling pathways directly controls the direction of knee and knuckle bending?&#10;A) FGF&#10;B) Shh&#10;C) Wnt&#10;D) Notch

Accepted Answer

The answer of Which of the following intercellular signaling pathways...

Question 6

Which mechanism underlies the formation of separate digits?&#10;A) FGF induces apoptosis of interdigital cells&#10;B) Lack of FGF induces necrosis of interdigital cells&#10;C) BMP induces apoptosis of interdigital cells&#10;D) Lack of BMP induces necrosis of interdigital cells

Accepted Answer

BMP (Bone Morphogenetic Protein) signaling is crucial for the apoptosis of interdigital cells, which leads to the separation of digits during limb development.

Question 7

Which axis in the Drosophila wing is inherited through engrailed expression from the embryonic parasegment?&#10;A) Antero-posterior&#10;B) Dorso-ventral&#10;C) Proximo-distal&#10;D) Left-right

Accepted Answer

The antero-posterior axis in the Drosophila wing is inherited through engrailed expression from the embryonic parasegment. Engrailed is a key gene involved in establishing this axis during development.

Question 8

Which of the following is synthesized along the antero-posterior wing boundary to act as a morphogen to cells in both compartments?&#10;A) Decapentaplegic (Dpp)&#10;B) Spalt (Sal)&#10;C) Brinker (Brk)&#10;D) Optomotorblind (Omb)

Accepted Answer

Decapentaplegic (Dpp) is synthesized along the antero-posterior wing boundary in Drosophila and acts as a morphogen, providing positional information to cells in both the anterior and posterior compartments of the wing.

Question 9

Which of the following tissues signals to the overlying ectoderm in a vertebrate embryo to induce the lens placode?&#10;A) Surface ectoderm&#10;B) Neural retina&#10;C) Cornea&#10;D) Optic vesicle

Accepted Answer

The optic vesicle, which is an outgrowth from the developing brain of the vertebrate embryo, signals to the overlying ectoderm to induce it to form the lens placode, which will eventually develop into the lens of the eye.

Question 10

Which of the following is not true of the pax6 gene?&#10;A) Loss of Pax6 function in humans leads to aniridia&#10;B) Ectopic pax6 expression induces eye development in non-eye imaginal discs&#10;C) Pax6 function is evolutionarily conserved&#10;D) It encodes a intercellular signaling receptor

Accepted Answer

Pax6 encodes a transcription factor, not an intercellular signaling receptor. This transcription factor is crucial for eye development and its function is highly conserved across species.

Deck 10: Organogenesis