Chapter 3

Question 1

mitosis

Answer 1

the process of cell division in which both resulting cells receive the full complement of genetic material

Question 2

pleiotropy

Answer 2

the phenomenon in which a single gene plays a role in several, seemingly unrelated traits

Question 3

redundancy

Answer 3

here, the phenomenon in which several genes play a role in a process such that loss of one may have a relatively minor effect

Question 4

mitotic figures

Answer 4

the tangled threads of duplicated chromosomes being pulled apart that are seen in cells undergoing mitosis

Question 5

meninges

Answer 5

the three layers of tissue protecting the vertebrate central nervous system

Question 6

pia mater

Answer 6

also called simply ‘pia.’ the innermost layer of the vertebrate meninges, found along the outer surface of the brain

Question 7

ventricular zone

Answer 7

the regions adjacent to the ventricles of the brain and central canal of the spinal cord, where cell division continues throughout life

Question 8

neuroblast

Answer 8

a cell that will divide to produce neural cells

Question 9

marginal zone

Answer 9

the outermost layer of the developing vertebrate brain. By adulthood it will form the molecular layer of the cerebral cortex

Question 10

neurogenesis

Answer 10

the mitosis of cells that will give rise to neurons

Question 11

gliogenesis

Answer 11

the mitosis of cells that will give rise to glia

Question 12

intermediate zone

Answer 12

the layer between the ventricular zone and marginal zone of the developing vertebrate brain

Question 13

glial fibrillary acidic protein (GFAP)

Answer 13

a structural protein normally expressed in radial glia and astrocytes but not neurons

Question 14

lacZ

Answer 14

a bacterial gene that encodes the enzyme beta-galactosidase

Question 15

beta-galactosidase (beta-Gal)

Answer 15

a bacterial enzyme, encoded by the lacZ gene, that often serves as a reporter gene or marker in studies of neural development

Question 16

Purkinje cells

Answer 16

the large, multi-polar neurons that form a single layer in the vertebrate cerebellar cortex

Question 17

internal granule layer

Answer 17

a layer of small neurons ventral to the Purkinje cell layer in the vertebrate cerebellar cortex

Question 18

external granule cell layer

Answer 18

a layer of granule neurons that migrate to the top of the developing cerebellum before migrating ventrally to form the internal granule cell layer in adulthood

Question 19

subventricular zone (SVZ)

Answer 19

the region just next to the ventricular zone, where many cells divide to provide neurons and glia to the developing vertebrate brain and, in at least some brain regions, new neurons in adulthood

Question 20

white matter

Answer 20

the inner portion of the vertebrate brain, consisting primarily of myelinated axons coursing to or from the cerebral cortex, hence light in color in postmortem preparations

Question 21

cortical plate

Answer 21

in developing cortex, the expanding layer of postmitotic cells that settle beneath the marginal zone and above the intermediate zone. it will form layers II-VI

Question 22

gray matter

Answer 22

the outer portion of the vertebrate brain, predominated by neuronal and glial cell bodies rather than myelin, hence dark in color in postmortem preparations. it is organized in six layers in mammals

Question 23

molecular layer

Answer 23

the outermost layer of the vertebrate cerebral cortex, consisting primarily of dendrites and axons with relatively few cell bodies

Question 24

neocortex

Answer 24

the six-layered outer region of the mammalian cerebral cortex

Question 25

birthdate

Answer 25

here, the time during development when a given cell underwent its final mitosis before differentiating into a neuron or glial cell

Question 26

thymidine

Answer 26

a nucleotide used in the synthesis of DNA. Because thymidine is not used in RNA, it can serve as a DNA-specific marker

Question 27

autoradiography

Answer 27

a process in which a tissue "takes its own picture" when photographic film is exposed to radioactively labeled markers

Question 28

5-bromo-2'-deoxyuridine (BrdU)

Answer 28

a synthetic nucleotide that can serve as a substitute for thymidine in the synthesis of DNA but can be readily distinguished from thymidine by the use of antibodies

Question 29

immunohistochemistry (IHC)

Answer 29

a method for detecting a particular protein in tissues in which an antibody recognizes and binds to the protein and then chemical methods are used to leave a visual reaction product around each antibody

Question 30

antibodies

Answer 30

large, Y-shaped proteins produced by the immune system that recognize and bind to particular shapes in molecules

Question 31

dam

Answer 31

here, a mother of a domesticated animal

Question 32

epitope

Answer 32

the particular shape of a molecule that a given antibody recognizes and binds

Question 33

radial glial cells

Answer 33

also called simply 'radial glia.' long, slender glial cells that stretch from the ventricular surface to the pial surface in the vertebrate cerebral cortex

Question 34

cortical preplate

Answer 34

the region between the ventricular zone and marginal zone in developing vertebral cerebral cortex, which develops into the gray matter of the neocortex

Question 35

ganglionic eminences (GEs)

Answer 35

transient bumps along the lateral ventricles of the developing telencephalon, from which neurons migrate tangentially across radial glia

Question 36

anosmia

Answer 36

the condition of being unable to detect odors

Question 37

rostral migratory stream (RMS)

Answer 37

a collection of cells that migrate from the anterior horn of the lateral ventricles to the olfactory bulbs in adult mammals

Question 38

subgranular zone

Answer 38

the portion of the dentate gyrus where cells divide in adulthood to contribute new neurons to the overlying granular layer

Question 39

peripheral nervous system (PNS)

Answer 39

the entire nervous system other than the central nervous system; it includes the enteric and autonomic nervous system. it is derived from neural crest cells

Question 40

pharyngeal arch 1

Answer 40

incus and malleus; mandible, maxilla, and temporal bone regions (from neural crest) maxillary and mandibular divisions of trigeminal nerve (V)

Question 41

pharyngeal arch 2

Answer 41

stapes bone of the middle ear; styloid process of temporal bone; part of hyoid bone of neck (all from neural crest) facial nerve (VII)

Question 42

pharyngeal arch 3

Answer 42

lower rim and greater horns of hyoid bone (from neural crest) glossopharyngeal nerve (IX)

Question 43

pharyngeal arch 4

Answer 43

laryngeal cartilages (from lateral plate mesoderm, not neural crest) superior laryngeal branch of vagus nerve (X)

Question 44

pharyngeal arch 6

Answer 44

laryngeal cartilages (from lateral plate mesoderm, not neural crest) recurrent laryngeal branch of vagus nerve (X)

Question 45

somites

Answer 45

paired blocks of mesoderm found on either side of the neural tube

Question 46

dorsal root ganglion (DRG)

Answer 46

a collection of neuron cell bodies embedded in vertebrate dorsal roots of the spinal cord that provides neurites to gather sensory information from the periphery and transmit it to the dorsal horn of the spinal cord

Question 47

autonomic ganglia

Answer 47

collections of neurons outside the central nervous system that provide autonomic innervation of body organs

Question 48

melanocytes

Answer 48

neural crest-derived pigment cells that provide color to the skin

Question 49

cell adhesion molecules (CAMs)

Answer 49

a class of molecules, found in extracellular regions, that adhere to some cells and not others

Question 50

neural cadherin (N-cadherin)

Answer 50

also called NCad. a family of calcium-dependent adhesion molecules

Question 51

collagen

Answer 51

a long-chained filamentous protein that contributes to the formation of extracellular matrix and is especially prominent in connective tissue

Question 52

laminin

Answer 52

a long-chained glycoprotein that readily binds other molecules and is a major component of the extracellular matrix and connective tissue

Question 53

fibronectin

Answer 53

a long-chained glycoprotein that contributes to the formation of the extracellular network

Question 54

basal lamina

Answer 54

a particularly thick layer of extracellular matrix that surrounds mature muscle fibers and many organs

Question 55

metalloproteases

Answer 55

enzymes that break down proteins and require atoms of a metal such as zinc to function

Question 56

ephrins

Answer 56

a family of membrane-bound signaling molecules that bind to ephrin receptors, which are part of the receptor tyrosine kinase (RTK) superfamily

Question 57

neural cell adhesion molecule (NCAM)

Answer 57

also called 'neural-cam.' an adhesive molecule expressed by many neurons

Question 58

Bergmann glia

Answer 58

long, slender glial cells in cerebellar cortex that guide neurons migrating from the external granule cell layer to the internal granule cell layer

Question 59

parallel fibers

Answer 59

the long axons from granule neurons of the cerebellum that innervate Purkinje neuron dendrites

Question 60

astrotactin

Answer 60

a gene that is expressed by cerebellar granule cells to help them to grip glial fibers for migration

Question 61

reelin

Answer 61

a gene that encodes the protein reelin and when dysfunctional, results in a very disorganized cerebellum and cerebrum in mice

Question 62

olfactory placode

Answer 62

a plate-shaped collection of cells outside the developing brain, from which cells migrate through the olfactory bulb and to the rest of the brain

Question 63

olfactory sensory neurons (OSNs)

Answer 63

the primary sensory neurons of the olfactory epithelium, which contact and recognize particular odorants

Question 64

olfactory bulb

Answer 64

an anterior projection of the brain that terminates in the upper nasal passages and, through small openings in the skull, receives axons from olfactory sensory neurons

Question 65

olfactory ensheathing glia (OEGs)

Answer 65

glia found in the olfactory epithelium that guide newly generated olfactory sensory neurons into place

Question 66

gonadotropin-releasing hormone (GnRH)

Answer 66

a protein released by neurons in the hypothalamus into the median eminence, which directs anterior pituitary cells to secrete the gonadotropins; follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

Question 67

Kallmann syndrome

Answer 67

a condition in which individuals fail to reach puberty and are unable to detect odors