Ch9

Question 1

Superficial cleavage

Answer 1

cleavage confined to the cytoplasmic rim

Question 2

Syncytial cytoplasm

Answer 2

all cleavage nuclei in a common cytoplasm

Question 3

Energids

Answer 3

nuclei and their associated cytoplasmic islands

Question 4

Nuclei move to the periphery in cycle

Answer 4

10

Question 5

Membrane develops around nuclei in cycle

Answer 5

13

Question 6

Cellular blastoderm

Answer 6

cells (nuclei + membrane) in a single layer around yolk core (around perimeter)

Question 7

Blastoderm cellularization involves

Answer 7

furrow canals

Question 8

Gastrulation

Answer 8

1. segregation of the mesoderm, ectoderm, and endoderm
2. mesoderm (at ventral midline) makes a ventral furrow - layer of mesoderm tissue beneath ventral ectoderm
3. endoderm invaginates - 2 pockets and anterior and posterior of the ends of the ventral furrow (pole cells to posterior pocket)
4. embryo bends –> cephalic furrow
5. ectoderm on surface and and mesoderm converge and extend, migrate to ventral midline to make the germ band
6. germ band extends posterioroly to the top (dorsal)
7. the nervous system forms from 2 regions of ventral ectoderm
8. specification of cell types along anteriorposterior and dorsal-ventral by interaction of cytoplasmic materials

Question 9

Distinguish the thoracic and abdominal regions by

Answer 9

differences in the cuticle

Question 10

Anterior and posterior form from

Answer 10

the position of the egg in the ovary

Question 11

Maternal effect genes

Answer 11

encode translational/transcriptional proteins that activate/repress the expression of zygotic genes

Question 12

Bicoid and Hunchback

Answer 12

maternal effect genes that regulate the production of anterior structures

Question 13

Nanos and Caudal

Answer 13

proteins that regulate the formation of posterior parts

Question 14

Zygotic genes include

Answer 14

gap, pair-rule, polarity, and homeotic sector genes

Question 15

Gap genes

Answer 15

make broad, overlapping segments

• divide the embryo into broad regions with several parasegment primordia

Question 16

Differing concentrations of gap genes cause trasncription of

Answer 16

pair-rule genes

Question 17

Pair-rule genes

Answer 17

• transcribed due to concentrations of gap genes
• divide the embryo into periodic units (7 vertical bands)
• subdivide the broad gap gene regions into parasegments

Question 18

Pair-rule genes activate the transcription of

Answer 18

segment polarity genes

Question 19

Segment polarity genes

Answer 19

mRNA and protein divide the embryo into 14 units, establishing periodicity
• responsible for maintaining certain repeated structures within each segment

Question 20

Homeotic selector genes are regulated by

Answer 20

the products of
• gap genes
• pair-rule genes
• segment polarity genes

Question 21

Homeotic selector genes

Answer 21

transcription determines the developmental fate of each segment

Question 22

Axes patterned before

Answer 22

nuclei begin to function

mRNA deposited

Question 23

Bicoid and hunchback are responsible for

Answer 23

head and thorax formation

Question 24

Nanos and caudal are responsible for

Answer 24

abdomen formation

Question 25

Tethered morphogens

Answer 25

bicoid and nanos

Question 26

Hunchback and caudal are found

Answer 26

throughout the embryo

Question 27

Fertilization leads to

Answer 27

translation of mRNAs to proteins

Question 28

Bicoid is high in

Answer 28

the anterior region | • inhibits translation of caudal (in the anterior)

Question 29

Nanos and pumilio bind

Answer 29

hunchback RNA | • no hunchback translation (in posterior)

Question 30

Bicoid binds

Answer 30

hunchback enhancer | and stimulates transcription

Question 31

The Bicoid, Hunchback, and Caudal proteins are

Answer 31

transcription factors whose concentration activates/represses zygotic genes (transcription)

Question 32

Anterior organizing center

Answer 32

Bicoid

Question 33

2 genes keep Bicoid

Answer 33

at anterior • exuperantia and swallow • absence = bicoid diffuses, less steep gradient, poorly formed head with extended mouth region

Question 34

Bicoid represses

Answer 34

translation of caudal RNA

Question 35

Bicoid is a

Answer 35

transcription factor that activates hunchback

Question 36

Genes for head formation need

Answer 36

* Bicoid for activation | * Hunchback for transcription

Question 37

Nanos inhibits

Answer 37

hunchback transcription in the posterior • hunchback bound by Pimilio • Pumilion joined by Nanos --> no hunchback translation in posterior

Question 38

Anterior and posterior termini

Answer 38

``` anterior = acron posterior = telson ```

Question 39

Torso gene

Answer 39

terminal gene • activated in the ends • found throughout

Question 40

Mutation in the torso gene leads to

Answer 40

no acron or telson

Question 41

The torso gene is activated by the

Answer 41

Torso-like protein • activates production of kinases that inactivate the transcriptional inhibitor of tailless and huckebin gap genes that specify the termini

Question 42

Terminal genes alone

Answer 42

both terminal regions telsons | • bicoid also present = 1 acron

Question 43

The anterior-posterior axis involves 3 sets of genes

Answer 43

* the anterior organizing center * the posterior organizing center * the terminal boundary region

Question 44

Cell fate commitment has 2 steps

Answer 44

1. specification | 2. determination

Question 45

Specification

Answer 45

a loose commitment | • flexible (can receive signals from environment eg morphogens)

Question 46

Determination

Answer 46

irreversible

Question 47

The transition from specification to determination is mediated by

Answer 47

segmentation genes

Question 48

Segmentation genes

Answer 48

genes that divide the early embryo into a repeating series of segmental primordia

Question 49

Mutations of segmentation genes often affect

Answer 49

parasegments

Question 50

Parasegments

Answer 50

regions of the embryo separated by mesodermal thickenings and ectodermal grooves • 14 in total

Question 51

A parasegment consists of

Answer 51

* the posterior of the anterior segment | * the anterior of the segment behind

Question 52

The transition from an embryo with gradients of morphogens into an embryo with distinct units is mediated by

Answer 52

gap genes

Question 53

Pair-rule genes are activated by

Answer 53

the products of gap genes interacting with products of neighboring gap genes

Question 54

Mutations of segment polarity genes leads to

Answer 54

a portion of each segment is deleted and replaced with a mirror image of another portion

Question 55

Segmentation genes are

Answer 55

transcription factors that use the gradients of the early cleavage embryo to transform the embryo into a periodic, parasegmental structure

Question 56

Homeotic selector genes are regulated by

Answer 56

gap and pair-rule genes

Question 57

Homeotic selector genes

Answer 57

determine the identity of each segment