Question 1

A man with recurrent respiratory infections and infertility is diagnosed with Kartagener syndrome.Mutations in the gene encoding which protein cause this syndrome?

Accepted Answer

Kartagener syndrome is usually caused by mutations in the gene encoding dynein, a protein essential for the movement of cilia and flagella. The dysfunction of cilia in Kartagener syndrome leads to recurrent infections in the respiratory tract and infertility in males. Surfactant, FGF8, BMP2, and insulin are not directly associated with this syndrome.

Question 2

A researcher knocks out the Tbx6 gene in a mouse.Which tissue will not form in the early embryo?

Accepted Answer

The Tbx6 gene is important for the formation of somites, which are blocks of mesoderm that give rise to muscle, bone, and cartilage in the developing embryo. Knocking out this gene would lead to a failure of somite formation. The other tissues listed (neural plate, notochord, lateral plate mesoderm, and endoderm) are not directly affected by the loss of Tbx6.

Question 3

A boy is admitted to the hospital for an emergency appendectomy.During surgery it is noted that the inflamed appendix is located on the left side,rather than the right side,and that the patient has situs inversus viscerum totalis.Mutations in which gene are known to cause this condition in animal models?

Accepted Answer

Mutations in the Pitx2 gene are known to cause situs inversus viscerum totalis in animal models.

Question 4

A researcher inactivates Lefty1,a gene expressed in the anterior visceral endoderm of the mouse.What effect would inactivation of this gene have on the gastrula-stage embryo?

Accepted Answer

Lefty1 acts as an inhibitor of Nodal signaling, which is crucial for primitive streak formation. Inactivating Lefty1 removes this inhibition, potentially leading to excessive Nodal signaling and the formation of extra primitive streaks.

Question 5

Patterning of the mesoderm involves so-called dorsalizing and ventralizing factors.Inactivation of which protein(s)in the early embryo would be expected to result in dorsalized mesoderm?

Accepted Answer

The answer of Patterning of the mesoderm involves so-called dorsalizing...

Question 6

Rieger syndrome,which affects development of both the teeth and eyes,results from haploinsufficiency in which gene in humans?

Accepted Answer

Rieger syndrome is caused by haploinsufficiency of the PITX2 gene, which plays a critical role in the development of teeth and eyes. This gene provides instructions for making a protein that regulates the activity of other genes involved in eye and tooth formation. Mutations in this gene result in a variety of eye abnormalities, such as glaucoma and cataracts, as well as dental anomalies, including missing or misshapen teeth.

Question 7

Alagille syndrome involves a failure of proper segmentation of the paraxial mesoderm,ultimately resulting in defects of the vertebral column.Which signaling pathway is mutated in patients with Alagille?

Accepted Answer

Alagille syndrome involves mutations in the Notch signaling pathway, specifically in the Notch ligand Jagged1. This leads to improper development of several organs, including the vertebral column.

Question 8

Which tissues ingress through the cranial end of the primitive streak?

Accepted Answer

The prospective cardiogenic mesoderm ingresses through the cranial end of the primitive streak during early embryonic development, contributing to the formation of the heart.

Question 9

In a classical experiment,a portion of an amphibian gastrula was transplanted to the belly region of another embryo,resulting in the formation of a secondary embryo organized by the graft from host tissue.The equivalent area of the human embryo that would be expected to have similar organizer activity is what structure?

Accepted Answer

The organizer activity in amphibian gastrula is due to a structure called the dorsal lip of the blastopore, which can induce the formation of a secondary embryo. The equivalent structure in humans is the node, which also plays a key role in organizing the developing embryo. The other choices (B) somites, (C) cardiac mesoderm, (D) cloacal membrane, and (E) body fold, do not have organizer activity similar to the dorsal lip of the blastopore or the node.

Question 10

Caudal dysplasia results from defects in which developmental process?

Accepted Answer

Caudal dysplasia is associated with defects in gastrulation, which is the process where the three germ layers form and establish the body plan, including the caudal structures.

Quiz 4: Third Week: Becoming Trilaminar and Establishing Body Axes