(1) The Making of a Body and a Field: Part 1

Question 1

zygote

Answer 1

single fertilized egg

Question 2

blastocyst

Answer 2

a ball of identical cells (same shape as enbryo bc cells aren’t growing, just dividing)

Question 3

what is developmental biology

Answer 3

the gradual process of change within cells and tissues of the body; it is directed by intrinsic and extrinsic factors; a process taking us from genotype to phenotype

Question 4

what are six stages of development?

Answer 4

1. fertilization
2. cleavage
3. gastrulation
4. organogenesis
5. metamorphosis
6. gametogenesis

Question 5

fertilization

Answer 5

fusion of haploid gametes (sperm and egg); results in a diploid zygote with unique genome

Question 6

cleavage

Answer 6

period of rapid mitotic cell division to produce multicellular blastula; cells of blastula are blastomeres

Question 7

gastrulation

Answer 7

period of cellular rearrangement to produce specialized tissues and organs

Question 8

metamorphosis

Answer 8

major alteration of body plan in a new hatchling or newborn that transforms a sexually immature larval form to a sexually mature adult (ex: tadpoles to frogs)

Question 9

gametogenesis

Answer 9

formation of haploid gametes by meiosis

Question 10

what is polarization when it comes to eggs

Answer 10

one side is different from the other

Question 11

animal pole

Answer 11

animal cap (brown; the white part is the nucleus); the majority of the frog

Question 12

vegetal pole

Answer 12

provides nutrients

Question 13

fertilization in Xenopus laevis (African clawed frog)

Answer 13

fertilization is external; mating is amplexus

Question 14

what does fertilization accomplish (3 things)

Answer 14

1. joins haploid sperm and egg
2. activates biochemical events in fertilized egg (ACTIVATION); allows the development of the embryo
3. cause rearrangements of cytoplasmic structures and contents in fertilized egg (set up axes of future organism)

Question 15

3 body axes of bilaterians

Answer 15

1. ant/post
2. dors/vent
3. left/right

Question 16

cleavage in Xenopus laevis (frog)

Answer 16

1. mitosis is very rapid so there is no growth between divisions; the embryo becomes multicellular but doesn’t grow bigger2
2. biphasic (M & S); no G1 or G2

Question 17

Gastrulation in Xenopus Laevis

Answer 17

1. cells on the surface involute (tuck into center)
2. create a dimple, called a blastopore
3. blastopore is initiated at a stop that denotes future dorsal side, so upper ridge of tissue is called dorsal blastopore lip
4. blastopore becomes deeper, but also extends laterally and ventrally

Question 18

Organogenesis in Xenopus Laevis: Neurulation

Answer 18

1. Neurulation is the formation of nervous system
2. forms on outside from ectoderm along dorsal midline
3. deepends to form a neural groove
4. circularizes to form a neural tube and is covered over by surface ectoderm

Question 19

3 primary germ layers

Answer 19

1. ectoderm
2. mesoderm
3. endoderm

present in embryos of all triploblastic animals; everything but sponges and comb jellies

Question 20

ectoderm

Answer 20

outermost layer; skin/nervous system

Question 21

mesoderm

Answer 21

middle layer; notochord, somites (vertebrae, muscle, dermis of skin), many internal organs

Question 22

endoderm

Answer 22

innermost layer; lining of digestive tract

Question 23

archenteron

Answer 23

primitive gut

Question 24

pre-hatching in Xenopus Laevis

Answer 24

embryo is curled and still enclosed in a transparent membrane called vitelline layer

Question 25

post-hatching oin Xenopus laevis

Answer 25

embryo breaks free of the vitelline layer and is a free-swimming tailbud-stage larva, which must eat

Question 26

Metamorphosis in Rana Pipiens

Answer 26

fully aquatic to terrestrial (added forelimbs, hindlimbs, smaller tail, lungs)

Question 27

Gametogenesis

Answer 27

1. is completed in adults 2. required for continuation of species 3. diploid precurose cells undergo meuosis to produce haploid sperm in males and haploid egg in females 4. completed in time for next mating season (spring)

Question 28

generalities about cleavage

Answer 28

1. rapid mitosis cell division without growth in between 2. cell cycle is biphasic (only M & S) 3. embryo grows no larger, just becomes multicellular with progressively smaller cells

Question 29

mid-blastula transition (still in blastula phase)

Answer 29

1. rate of mitotic cleavage slows 2. cell cycle lengthens to include G1 and G2 (cell now actually grows) 3. progression through diff. phases reguated by diff. conbos of cdk's and their associated cyclins 4. cdk's and cyclins that function after mid-blastula transition are synthesized from genome (not from stores mRNAs or original egg cytoplasm)

Question 30

cleavage patterns

Answer 30

dependent upon the amount and distribution of yolk holoblastic (isolecithal, mesolecithal); meroblastic (teloecthial, centrolecithal) dependent upon angle of mitotic spindle and timing of its formation (x,y,z axis)

Question 31

holoblastic

Answer 31

the entire yolk is cleaved

Question 32

meroblastic

Answer 32

the yolk isn't entirely cleaved bc of DENSE yolk

Question 33

isolecithal

Answer 33

sparse yolk, evenly distributed humans

Question 34

mesolecithal

Answer 34

moderate yolk, deposited at vegetal pole

Question 35

telocithal

Answer 35

dense yolk throughout most of egg chickens

Question 36

centrolecithal

Answer 36

dense yolk, centrally located most insects

Question 37

influence of yolk

Answer 37

1. dense yolk impedes cleavage 2. cleavage of entire egg proceeds unimpeded in isolecithal egg 3. cleavage of the vegetal pole in mesolecithal eggs (amphibians) occurs at a slower rate 4. cleavage of the vegetal pole does not occur at all in telolecithal eggs (chick) 5. superficial cleavage occurs in centrolecithal eggs (insects)

Question 38

cleavage pattern of sea urchin and starfish (echinoderms)

Answer 38

radial but isolecithal

Question 39

cleavage pattern of mammals

Answer 39

rotational but isolecithal

Question 40

cleavage pattern of amphibians

Answer 40

displaced radial cleavage but mesolecithal

Question 41

cleavage pattern of birds/chick

Answer 41

discoidal cleavage but telolecithal

Question 42

cleavage pattern of insects/drosophila

Answer 42

superficial cleavage but centrolecithal

Question 43

2 major cell types in early embryos

Answer 43

epithelial and mesenchymal

Question 44

epithelial cells in early embryo

Answer 44

1. tightly packed into sheets 2. cells are connected to each other via tight junctions 3. serve as a barrier function 4. ex: skin

Question 45

mesenchymal cells in early embryo

Answer 45

1. cells are not connected to each other; allows them to move 2. not tightly packed 3. migratory 4. ex: microglia, macrophages

Question 46

surprising early discoveries from anatomical studies

Answer 46

1. cells move around in embryo- sometimes great distances 2. cells grow 3. cells change shape 4. cell divisions differ in number and in plane of orientation 5. certain large subsets of cels selectively die (apoptosis) 6. cells differ in membrane components and in secreted products

Question 47

types of cell movement during gastrulation

Answer 47

1. invagination 2. involution 3. ingression 4. delamination 5. epiboly