Question 1

Weaver mice provide insight into mechanisms of cerebellar development.What gene is mutated in these mice?

Accepted Answer

The gene mutated in weaver mice is Girk2 (G protein-activated inward rectifier potassium channel 2). This mutation leads to the characteristic neurological defects observed in these mice, providing insights into cerebellar development and function.

Question 2

A child is diagnosed with Kallmann syndrome.Genetic evaluation revealed a mutation in the patient of the KAL1 gene.What does this gene encode?

Accepted Answer

The KAL1 gene encodes for anosmin-1, a protein necessary for the development of the olfactory and reproductive systems. Mutations in this gene result in Kallmann syndrome, which is characterized by hypogonadotropic hypogonadism and anosmia (loss of sense of smell).

Question 3

A researcher interested in patterning of the early neural tube identifies a new secreted factor expressed in the floor plate.Assuming that the newly identified factor plays a role in patterning,which axis of the developing neural tube would you expect to be perturbed if this factor is inactivated?

Accepted Answer

The newly identified secreted factor expressed in the floor plate is likely involved in dorsal-ventral patterning of the neural tube. Inactivation of this factor would perturb the dorsal-ventral axis.

Question 4

A researcher knocks out Ephrin-B2 in the developing visual system.What effect will this have on retinal ganglion cell (RGC)axon projection?

Accepted Answer

Ephrin-B2 is involved in guiding retinal ganglion cell (RGC) axons to their correct targets in the visual system. Normally, Ephrin-B2 and its receptors help to establish the correct balance of ipsilateral and contralateral projections. Knocking out Ephrin-B2 disrupts this guidance, leading to RGC axons projecting contralaterally instead of their normal ipsilateral or contralateral projection pattern.

Question 5

An investigator injects a cell lineage marker into the developing ventricular zone of the ganglionic eminence of the developing forebrain.Cells in which region of the neonatal brain will be labeled?

Accepted Answer

The ganglionic eminence gives rise to the basal ganglia. Therefore, the injected cell lineage marker will label cells in the basal ganglia region of the neonatal brain.

Question 6

A 45-year-old man develops Bell's palsy in which function of the facial (VII)cranial nerve is compromised.What specific level of the central nervous system does the facial nerve connect to?

Accepted Answer

The facial nerve (cranial nerve VII) connects to the brainstem at the level of the metencephalon, which includes the pons and the cerebellum. This area is responsible for transmitting nerve signals that control facial expressions, among other functions.

Question 7

A 4-year-old girl is diagnosed with cerebellar heterotopia.What developmental process likely went awry,accounting for heterotopia?

Accepted Answer

Cerebellar heterotopia is a condition in which the cells meant to migrate to the cerebellum during brain development are misplaced and end up in abnormal locations. This indicates that there was a problem with cell migration during development.

Question 8

A 3-year-old boy with spina bifida develops hydrocephalus.What is the likely cause of this?

Accepted Answer

Hydrocephalus in spina bifida is usually caused by a blockage of the median or lateral apertures, which results in a buildup of cerebrospinal fluid (CSF). CSF is produced by the choroid plexus and flows through the ventricles of the brain before exiting through these apertures into the subarachnoid space. In spina bifida, the abnormal spinal cord can cause a blockage of these apertures, leading to hydrocephalus.

Question 9

A researcher interested in patterning of the early neural tube identifies a new secreted factor expressed in the isthmus signaling center.Assuming that the newly identified factor plays a role in patterning,which axis of the developing neural tube would you expect to be perturbed if this factor is inactivated?

Accepted Answer

The isthmus signaling center is crucial for patterning along the cranial-caudal (anterior-posterior) axis of the developing neural tube, influencing the development of midbrain and hindbrain structures. Inactivating a factor expressed in this region would likely disrupt cranial-caudal patterning.

Question 10

A 13-year-old girl develops a tumor of the anterior pituitary gland.What is the embryologic origin of the anterior pituitary gland?

Accepted Answer

The anterior pituitary gland develops from Rathke's pouch, which is an invagination of the oral ectoderm that forms during embryonic development.

Question 11

A researcher knocks out the Soho gene in the rudiment of the developing mouse eye.What aspect of eye development will be affected?

Accepted Answer

The Soho gene is known to be involved in the differentiation of the nasal and temporal regions of the neural retina. Therefore, knocking out this gene would likely affect the development of the nasal-temporal axis of the neural retina.

Question 12

A 20-year-old woman suffers a stroke after a drug overdose that causes localized damage to the brain stem special somatic afferent column on one side.Sensation from which structure(s)will be compromised?

Accepted Answer

The inner ear is part of the special somatic afferent column, which is damaged in the brain stem in this scenario. Sensory information related to hearing and balance is transmitted through the inner ear, meaning that sensation from this structure will be compromised. The other structures listed are not part of the special somatic afferent column and would therefore not be affected by this type of brain stem damage.

Question 13

A surgeon operates on the lumbar nervous system to relieve intractable pain in a terminal cancer patient.What specific part of the nervous system would be cut?

Accepted Answer

The dorsal root carries sensory information from the peripheral nervous system to the spinal cord. By cutting the dorsal root, the sensory information from the cancerous area would not be transmitted to the brain, thus relieving the intractable pain. It is important to note that this procedure, known as dorsal rhizotomy or dorsal root entry zone (DREZ) lesioning, is a palliative measure and will not cure the underlying disease.

Question 14

A researcher labels a small area of the neural tube at the future cerebellar level.It is later noted that cells in the deep cerebellar nuclei are labeled.What portion of the neural tube was labeled in this experiment?

Accepted Answer

The answer of A researcher labels a small area of...

Question 15

A researcher treats an early neural-tube-stage embryo with a 1-hour pulse of colchicine,which arrests proliferating cells in metaphase.Where will the arrested cells be found?

Accepted Answer

The ventricular layer of the neural tube is where the cells are actively dividing during the early stages of embryonic development. Colchicine, which arrests cells in metaphase, would affect cells in this layer. The marginal and mantle layers are formed by cells that have migrated out of the ventricular layer, so they would not be affected by the treatment. The floor and roof plates are specialized regions of the neural tube that play important roles in development, but do not have a high concentration of proliferating cells.

Quiz 10: Development of the Central Nervous System