Question 1

Researchers have shown that the Hox genes are important for patterning the pharyngeal arches.Which of the Hox genes is essential for the specification of the second pharyngeal arch and when genetically inactivated in mice,result in the homeotic transformation of the second pharyngeal arch into one with first pharyngeal arch identity?

Accepted Answer

Hoxa2 is essential for the specification of the second pharyngeal arch and genetic inactivation in mice leads to the transformation of the second pharyngeal arch into one with first pharyngeal arch identity.

Question 2

Mutations in the growth factor SONIC HEDGEHOG would be expected to result in which birth defect?

Accepted Answer

Mutations in the growth factor SONIC HEDGEHOG are associated with Holoprosencephaly, a birth defect characterized by incomplete separation of the forebrain during embryonic development. Cleft lip, cleft palate, craniosynostosis, and mandibulofacial dysostosis are associated with other genetic and environmental factors.

Question 3

Both cleft lip and palate have a genetic component,which results in differences in the frequency of cleft lip and palate in females and males.Does cleft lip occur more often in females or males?

Accepted Answer

Cleft lip occurs more often in males due to the fact that it is a sex-linked genetic trait carried on the X chromosome. Males have only one X chromosome, which means they have a higher chance of inheriting the trait if it is present on their X chromosome. Females have two X chromosomes, so if the trait is present on one X chromosome, it may be masked by the other X chromosome that does not carry the trait.

Question 4

Van der Woude syndrome is predominantly characterized by which defect?

Accepted Answer

Van der Woude syndrome is predominantly characterized by a defective outgrowth of the facial processes, specifically cleft lip and/or cleft palate. It is caused by mutations in the IRF6 gene, which plays a crucial role in facial development. Other features may include lip pits and hypodontia (missing teeth).

Question 5

Fate mapping studies of neural crest cell migration have been carried out in chicks,quails,and mice.These studies have shown that the neural crest cells that populate the second pharyngeal arch arise from which level(s) of the brain?

Accepted Answer

The answer of Fate mapping studies of neural crest cell...

Question 6

The oropharyngeal membrane ruptures to create the continuity between the developing gut and oral cavity during which week of gestation?

Accepted Answer

The oropharyngeal membrane ruptures during the 5th week of gestation, creating the oral cavity's connection to the developing gut.

Question 7

Which signaling molecule patterns the cranial-caudal axis of the hindbrain?

Accepted Answer

Retinoic acid patterns the cranial-caudal axis of the hindbrain.

Question 8

The muscles of mastication,excluding the tongue muscles,arise from the mesoderm of which structure(s)?

Accepted Answer

The muscles of mastication arise from the mesoderm of the first pharyngeal arches.

Question 9

Researchers have shown that the mandibular prominence can be transformed into the maxillary prominence by the genetic inactivation of two homeobox transcription factors in mice.What are these two factors?

Accepted Answer

The two homeobox transcription factors whose genetic inactivation can transform the mandibular prominence into the maxillary prominence in mice are Dlx5 and Dlx6.

Question 10

The muscles of facial expression arise from the mesoderm of which structure(s)

Accepted Answer

The answer of The muscles of facial expression arise from...

Question 11

The developing hindbrain is segmented into rhombomeres,which are characterized by the differential expression of members of the Hox family of transcription factors.Researchers have shown that some members of the Hox family are crucial for the specification of the rhombomeres.When Hoxa1 is genetically inactivated in mice,which rhombomeres are affected?

Accepted Answer

The answer of The developing hindbrain is segmented into rhombomeres,which...

Question 12

Neural crest cells migrate from the hindbrain in distinct streams.How many neural crest cells streams are there in the hindbrain?

Accepted Answer

There are three distinct streams of neural crest cells that migrate from the hindbrain during development.

Question 13

The stylopharyngeus muscle is innervated by which nerve?

Accepted Answer

The stylopharyngeus muscle is innervated by the glossopharyngeal nerve (CN IX).

Question 14

The third pharyngeal arch artery gives rise to which adult blood vessel(s)?

Accepted Answer

The third pharyngeal arch artery gives rise to the common carotids and the roots of the internal carotids.

Question 15

At birth what is the approximate ratio of the facial skeleton to the cranial vault?

Accepted Answer

At birth, the approximate ratio of the facial skeleton to the cranial vault is 1:7. This means that the facial bones only make up a small portion of the skull at birth, and the cranial vault is much larger in size in proportion to the facial bones.

Quiz 17: Development of the Pharyngeal Apparatus and Face