Chapter 2

Question 1

vital dyes

Answer 1

relatively nontoxic synthetic dyes that can be used to label living cells

Question 2

fate map

Answer 2

a representation of which parts of an embryo will give rise to various parts of the adult body

Question 3

syncytium

Answer 3

a single cell containing several nuclei

Question 4

cellularization

Answer 4

the process in which cell walls are formed between the nuclei in a syncytium

Question 5

bicoid

Answer 5

a transcription factor that is concentrated in the presumptive anterior end of the embryo and directs formation of the head

Question 6

nanos

Answer 6

a transcription factor that is concentrated in the presumptive posterior end of the embryo

Question 7

maternal polarity genes

Answer 7

a class of genes provided by the mother such that their products are unevenly distributed in the zygote and thereby specify the anterior-posterior axis

Question 8

hunchback

Answer 8

a transcription factor that is one of the class of gap genes that is inhibited by the nanos protein

Question 9

gap genes

Answer 9

genes that encode a class of transcription factors, the expression of which is regulated by maternal polarity genes

Question 10

pair-rule genes

Answer 10

genes that encode a class of transcription factors, the expression of which is regulated by gap genes

Question 11

segment polarity genes

Answer 11

genes that encode a class of signaling factors, the expression of which is regulated by pair-rule genes

Question 12

homeotic selector genes or Hox genes

Answer 12

also called simply ‘homeotic genes.’ a class of genes in which mutations tend to result in swapping out one body part for another, as when mutation of Antennapedia results in the formation of legs where antennae normally form

Question 13

Antennapedia

Answer 13

a Hox gene in which mutations result in the formation of a leg where an antenna normally forms

Question 14

halteres

Answer 14

paired structures that serve as counterweights to maintain balance in the flight of some flies

Question 15

bithorax

Answer 15

a Hox gene in which mutations can result in the doubling of the thorax in Drosophila

Question 16

Ultrabithorax

Answer 16

a Hox gene complex that affects the fate of cells in the thorax of Drosophila

Question 17

homeobox

Answer 17

a nucleotide sequence that produces a DNA-binding domain in many transcription factor proteins. It is found in Hox genes and many other transcription factors

Question 18

realizator genes

Answer 18

a class of genes, the expression of which is controlled by Hox genes, that direct the actual construction of particular body parts

Question 19

colinearity

Answer 19

the property of Hox genes in which their order on the chromosome matches the order in which they are expressed along the anterior-posterior axis of the body

Question 20

gene duplication and divergence

Answer 20

the evolutionary process by which a gene duplication is followed by successive divergence in the sequence and function of the two copies

Question 21

prosencephalon

Answer 21

also called ‘forebrain.’ the most anterior aspect of the embryonic vertebrate brain. it will develop into the telencephalon and diencephalon

Question 22

mesencephalon

Answer 22

also called ‘midbrain.’ the middle segment of the embryonic vertebrate brain. it will develop into the adult midbrain

Question 23

rhombencephalon

Answer 23

also called ‘hindbrain.’ the caudal-most segment of the embryonic vertebrate brain. it will develop into the metencephalon (pons and cerebellum) and myelencephalon (medulla)

Question 24

telencephalon

Answer 24

the anterior-most portion of the vertebrate brain, consisting of the cerebral cortex and related subcortical structures such as the basal ganglia and hippocampus

Question 25

diencephalon

Answer 25

the portion of the vertebrate brain that consists of the thalamus and hypothalamus

Question 26

pons

Answer 26

the portion of the brainstem caudal to the midbrain, to which the cerebellum is attached

Question 27

cerebellum

Answer 27

a brain region attached to the pons that plays an important role in coordination of movement

Question 28

metencephalon

Answer 28

a subdivision of the hindbrain that includes the cerebellum and the pons

Question 29

myelencephalon

Answer 29

also called 'medulla.' the caudal-most portion of the vertebrate brainstem, which blends into the rostral spinal cord

Question 30

Otx2

Answer 30

a homeobox gene required for the development of the vertebrate midbrain and forebrain

Question 31

fibroblast growth factors (FGFs)

Answer 31

a family of proteins that act upon a family of receptor tyrosine kinase (RTK) receptors. they are concentrated in the posterior portions of the developing vertebrate nervous system and demarcate the midbrain/hindbrain junction

Question 32

Emx2

Answer 32

a homeobox gene highly expressed in the posterior portion of the developing vertebrate cortex

Question 33

Pax6

Answer 33

a homeobox gene highly expressed in the anterior portion of the developing vertebrate cortex

Question 34

rhombomeres

Answer 34

a group of prominently segmented portions of the embryonic rhombencephalon

Question 35

ephrins

Answer 35

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

Question 36

spontaneous abortion

Answer 36

the accidental loss of an embryo, sometimes called a miscarriage

Question 37

rostral

Answer 37

referring to the head end

Question 38

caudal

Answer 38

referring to the tail end

Question 39

mitogen

Answer 39

a substance that promotes mitosis

Question 40

Frizzled

Answer 40

a cell surface receptor protein that responds to Wnt

Question 41

Wnt

Answer 41

a gene that encodes the secreted protein Wnt, which is concentrated in the posterior end of vertebrate embryos

Question 42

retinoic acid (RA)

Answer 42

a steroid-like molecule, concentrated in the posterior end of vertebrate embryos, that promotes development of posterior structures. it is a powerful teratogen

Question 43

retinoic acid receptor (RAR)

Answer 43

a member of the steroid receptor superfamily that serves as a receptor for retinoic acid

Question 44

retinoic acid response element (RARE)

Answer 44

a specific sequence of DNA nucleotides that is bound by the retinoic acid-retinoic acid receptor complex, thereby regulating expression of the associated gene

Question 45

teratogen

Answer 45

a substance that causes malformations in development

Question 46

notochord

Answer 46

an embryonic rod-shaped structure that is derived from mesodermal tissue in all vertebrates and that induces formation of the ventral neural tube above

Question 47

motor neurons

Answer 47

neurons that send axons out to the periphery to innervate and control muscles

Question 48

signal peptide

Answer 48

a particular sequence of N-terminal amino acids that directs the full protein to the cell's secretory pathway

Question 49

Sonic hedgehog (Shh)

Answer 49

a gene that encodes the signaling protein that is secreted by the notochord and induces formation of the floor plate and the differentiation of motor neurons in the vertebrate neural tube

Question 50

floor plate

Answer 50

the ventral portion of the vertebrate neural tube, the developing spinal cord

Question 51

roof plate

Answer 51

the dorsal portion of the vertebrate neural tube