ch. 47 development Flashcards

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1
Q

when does a human embryo show development of distinctive features

A

5 weeks

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2
Q

fertilization

A

formation of diploid zygote from a haploid egg and sperm

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3
Q

events at egg surface during fertilization

A
  • sperm penetrate protective layer around egg
  • receptors on egg surface bind to molecules on sperm surface
  • changes at egg surface prevent polyspermy
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4
Q

polyspermy

A

entry of multiple sperm nuclei into the egg

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5
Q

acrosomal reaction

A

acrosome at tip of sperm releases hydrolytic enzymes that digest material surrounding egg

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6
Q

when is acrosomal reaction triggered

A

when sperm meets the egg

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7
Q

fast block to polyspermy

A

gamete contact/fusion depolarizes egg cell membrane

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8
Q

what initiates the cortical reaction

A

fusion of egg and sperm

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9
Q

what happens during the cortical reaction seconds after the sperm binds to the egg

A

vesicles beneath egg plasma membrane release contents to form fertilization envelope

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10
Q

slow block to polyspermy

A

fertilization envelope

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11
Q

cortical reaction and fertilization envelope

A
  • requires high concentration of Ca2+ in egg
  • reaction triggered by change in Ca2+ concentration
  • Ca2+ spread across egg correlates w/ appearance of fertilization envelope
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12
Q

what does the rise in Ca2+ in the cytosol of the egg increase

A

rates of cellular respiration and protein synthesis

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13
Q

how is egg activated

A

with the rapid changes in metabolism

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14
Q

where are the proteins and mRNAs needed for egg activation

A

already present in the egg

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15
Q

where is fertilization in mammals and other terrestrial animals

A

internal

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16
Q

what must sperm travel through to reach zona pellucida

A

layer of follicle cells surrounding egg

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17
Q

zona pellucida

A

extracellular matrix of egg

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18
Q

what does sperm binding trigger

A

cortical reaction

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19
Q

when does first cell division occur in mammals

A

12-36 hours after sperm binding

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20
Q

what is fertilization followed by

A

cleavage

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21
Q

cleavage

A

period of rapid cell division without growth

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22
Q

what does cleavage partition the cytoplasm of a large cell into

A

many smaller cells called blastomeres

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23
Q

blastula

A

ball of cells w/ fluid-filled cavity called a blastocoel

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24
Q

cleavage pattern in frogs and many other land animals

A

asymmetric due to distribution of yolk

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25
Q

yolk

A

stored nutrients

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26
Q

2 poles of cleavage pattern

A
  • vegetal
  • animal
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27
Q

vegetal pole

A

has more yolk

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28
Q

animal pole

A

has less yolk

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29
Q

cleavage furrows in frog

A
  • first 2: form 4 equally sized blastomeres
  • third: asymmetric due to yolk in vegetal hemisphere, unequally-sized blastomeres
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30
Q

holoblastic cleavage

A

complete division of the egg
- in species whose eggs have little or moderate amounts of yolk
- sea urchins and frogs

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31
Q

mesoblastic cleavage

A

incomplete division of the egg
- in species with yolk-rich eggs
- reptiles and birds

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32
Q

cleavage in Drosophila and other insects

A

multiple rounds of mitosis w/o cytokinesis

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33
Q

morphogenesis

A

process by which cells occupy their appropriate locations

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34
Q

what does morphogenesis involve

A
  1. gastrulation
  2. organogenesis
35
Q

gastrulation

A

rearranges cells of blastula into a 3-layered embryo called a gastrula

36
Q

3 layers produced by gastrulation

A
  1. ectoderm
  2. endoderm
  3. mesoderm
37
Q

ectoderm

A

forms outer layers, for frogs:
- epidermis of skin and derivatives
- nervous/sensory systems
- pituitary gland/adrenal medulla
- jaws/teeth

38
Q

endoderm

A

lines digestive tract, for frogs:
- epithelial lining of digestive tract/organs, respiratory/excretory/reproductive tracts lining
- thymus, thyroid, parathyroid glands

39
Q

mesoderm

A

partly fills space between endoderm and ectoderm, for frogs:
- skeletal/muscle systems
- circulatory/lymphatic systems
- excretory and reproductive systems
- dermis of skin
- adrenal cortex

40
Q

frog gastrulation

A
  • group of cells on dorsal side of blastula begin to invaginate
  • cells move from embryo surface into embryo by involution
  • cells become endoderm/mesoderm
  • cells on surface form ectoderm
  • newly formed cavity is archenteron
  • archenteron opens through blastopore (anus)
41
Q

what is chick embryo composed of prior to gastrulation

A

upper and lower layer: epiblast and hypoblast

42
Q

what happens during gastrulation of chicks

A
  • epiblast cells move toward midline of blastoderm and then into the embryo toward the yolk
  • midline thickens to form primitive streak
  • hypoblast cells contribute to sac that surrounds yolk and connection between yolk and embryo
43
Q

yolk in human eggs

A

very little

44
Q

human equivalent of blastula

A

blastocyst

45
Q

inner cell mass

A

cluster of cells at one end of the blastocyst

46
Q

trophoblast

A

outer epithelial layer of the blastocyst
- doesn’t contribute to embryo, instead initiates implantation

47
Q

what happens after implantation

A

trophoblast continues to expand, set of extraembryonic membranes is formed

48
Q

purpose of extraembryonic membranes

A
  • enclose specialized structures outside of the embryo
  • provide life-support system for further development of embryo
49
Q

what does gastrulation involve in humans

A

inward movement from the epiblast through a primitive streak, similar to chick embryo

50
Q

how long after fertilization does the blastocyst implant in humans

A

7 days

51
Q

how long after fertilization do the extraembryonic membranes form in humans

A

10-11 days

52
Q

how long after fertilization does the gastrulation occur in humans

A

13 days

53
Q

4 extraembryonic membranes

A

amnion, chorion, yolk sac, allantois

54
Q

reproduction outside of aqueous environments required development of

A
  • shelled egg of birds, reptiles, and monotremes
  • uterus of marsupial and eutherian mammals
55
Q

what are embryos surrounded by

A

fluid in a sac called the amnion
- allows reproduction on dry land

56
Q

amniotes

A

mammals, reptiles, and birds - embryos all in amnion

57
Q

chorion

A

gas exchange

58
Q

amnion

A

encloses amniotic fluid

59
Q

yolk sac

A

encloses yolk

60
Q

allantois

A

disposes of waste products and contributes to gas exchange

61
Q

organogenesis

A

various regions of germ layers develop into rudimentary organs

62
Q

neurulation

A

formation of brain and spinal cord in vertebrates

63
Q

how does neurulation begin?

A
  • cells from dorsal mesoderm form notochord
  • signaling molecules secreted by notochord/tissues cause ectoderm above to form neural plate (induction)
64
Q

notochord

A

rod extending along dorsal side of embryo

65
Q

induction

A

when cells or tissues cause a developmental change in nearby cells

66
Q

what does an inward curving of the neural plate form

A

neural tube

67
Q

what does the neural tube become

A

central nervous system

68
Q

what happens to the notochord before birth

A

disappears, but contributes to parts of the disks between vertebrae

69
Q

4 families of cell adhesion molecules

A
  1. cadherin
  2. Ig family
  3. selectin
  4. integrin
70
Q

where do neural crest cells develop

A

along neural tube of vertebrates and migrate in body to form parts of embryo

71
Q

what parts of the embryo will neural crest cells form

A

nerves, parts of teeth, and skull bones

72
Q

somites

A

blocks of mesoderm lateral to the notoochord

73
Q

what do parts of somites dissociate to form?

A

mesenchyme cells, which form the vertebrae, ribs, and muscles associated with vertebral column

74
Q

what is early organogenesis in the chick similar to

A

early organogenesis in the frog
- 3 days old, rudiments of major organs apparent

75
Q

what are the pattern and appearance of organogenesis in invertebrates different from?

A

that in vertebrates
- mechanisms of organogenesis (neurulation) are similar

76
Q

what are essential to movement and cell shape?

A

microtubules and microfilaments of cytoskeleton

77
Q

common mechanism fro invaginating cell layer

A

reorganizing cytoskeleton (like contraction of actin filaments)

78
Q

apoptosis

A

programmed cell death

79
Q

what happens to extra neurons that are produced during embryonic development?

A

eliminated by apoptosis

80
Q

what happens to tail of tadpole during metamorphosis

A

apoptosis

81
Q

determination

A

refers to process by which a cell/group of cells become committed to particular fate

82
Q

differentiation

A

refers to resulting specialization in structure and function

83
Q

do cells in a multicellular organism have the same or different genome?

A

same - difference comes from expression of different sets of genes