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Cell Bio & Developmental Genetics > Ch9 > Flashcards

Flashcards in Ch9 Deck (57):
1

Superficial cleavage

cleavage confined to the cytoplasmic rim

2

Syncytial cytoplasm

all cleavage nuclei in a common cytoplasm

3

Energids

nuclei and their associated cytoplasmic islands

4

Nuclei move to the periphery in cycle

10

5

Membrane develops around nuclei in cycle

13

6

Cellular blastoderm

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

7

Blastoderm cellularization involves

furrow canals

8

Gastrulation

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

9

Distinguish the thoracic and abdominal regions by

differences in the cuticle

10

Anterior and posterior form from

the position of the egg in the ovary

11

Maternal effect genes

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

12

Bicoid and Hunchback

maternal effect genes that regulate the production of anterior structures

13

Nanos and Caudal

proteins that regulate the formation of posterior parts

14

Zygotic genes include

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

15

Gap genes

make broad, overlapping segments
• divide the embryo into broad regions with several parasegment primordia

16

Differing concentrations of gap genes cause trasncription of

pair-rule genes

17

Pair-rule genes

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

18

Pair-rule genes activate the transcription of

segment polarity genes

19

Segment polarity genes

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

20

Homeotic selector genes are regulated by

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

21

Homeotic selector genes

transcription determines the developmental fate of each segment

22

Axes patterned before

nuclei begin to function
(mRNA deposited)

23

Bicoid and hunchback are responsible for

head and thorax formation

24

Nanos and caudal are responsible for

abdomen formation

25

Tethered morphogens

bicoid and nanos

26

Hunchback and caudal are found

throughout the embryo

27

Fertilization leads to

translation of mRNAs to proteins

28

Bicoid is high in

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

29

Nanos and pumilio bind

hunchback RNA
• no hunchback translation (in posterior)

30

Bicoid binds

hunchback enhancer
and stimulates transcription

31

The Bicoid, Hunchback, and Caudal proteins are

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

32

Anterior organizing center

Bicoid

33

2 genes keep Bicoid

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

34

Bicoid represses

translation of caudal RNA

35

Bicoid is a

transcription factor that activates hunchback

36

Genes for head formation need

• Bicoid for activation
• Hunchback for transcription

37

Nanos inhibits

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

38

Anterior and posterior termini

anterior = acron
posterior = telson

39

Torso gene

terminal gene
• activated in the ends
• found throughout

40

Mutation in the torso gene leads to

no acron or telson

41

The torso gene is activated by the

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

42

Terminal genes alone

both terminal regions telsons
• bicoid also present = 1 acron

43

The anterior-posterior axis involves 3 sets of genes

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

44

Cell fate commitment has 2 steps

1. specification
2. determination

45

Specification

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

46

Determination

irreversible

47

The transition from specification to determination is mediated by

segmentation genes

48

Segmentation genes

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

49

Mutations of segmentation genes often affect

parasegments

50

Parasegments

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

51

A parasegment consists of

• the posterior of the anterior segment
• the anterior of the segment behind

52

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

gap genes

53

Pair-rule genes are activated by

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

54

Mutations of segment polarity genes leads to

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

55

Segmentation genes are

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

56

Homeotic selector genes are regulated by

gap and pair-rule genes

57

Homeotic selector genes

determine the identity of each segment