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bio > Lecture 16: Development I > Flashcards

Lecture 16: Development I Flashcards

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Biology 101 flashcards
1
Q

development

A

all the changes that occur during a life cycle

embryonic, goes on after birth/ hatching

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2
Q

model organisms

A

species chosen for reasearch - easily studied

ex: roundworms, sea urchins, frogs , chicks

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3
Q

fertilization

A
  • sperm ( usually flagellated, motile + ovum (large, nonmotile -> zygote
  • haploid + diploid = diploid zygote
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4
Q

what are some consequences of fertilization

A
  • restores diploid # (2n)
  • determine sex of organisms
  • activates egg & stimulates reactions to promoting development
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5
Q

what is the egg surrounded by?

A

plasma membrane, 1+ coverings

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6
Q

what is the purpose of the coverings of the egg

A
  • aids in fertilization ( may secrete to signals to sperm cells
  • barrier to interspecific fertilization, important for external fertilization
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7
Q

steps of fertilization

A
  1. sperm dissolves protective layers in order to reach plasma membrane
  2. binds to receptors of egg surface ( ensures egg and sperm are same species)
  3. changes to egg surface - prevents polyspermy ( prevents multiple sperms from entering)
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8
Q

sea urchin egg coverings

A
  1. plasma membrane - innermost
  2. vitelline layer - thin
  3. jelly coat - thick glycoprotein layer
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9
Q

acrosome

A

releases hydrolytic enzymes

-partially digest jelly coat

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10
Q

acrosomal process

A
  • actin filaments
  • protrude from sperm head & penetrate jelly coat proteins at tip
  • bind to specific receptors on egg plasma membrane
  • ( lock and key) ensures same species
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11
Q

polyspermy

A
  • fertilization of egg by more than one sperm
  • offspring with extra chromosome sets
  • usually lethal
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12
Q

what happened when gametes are released into water

A
  • jelly coat releases chemicals into H20 -> attracts sperm
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13
Q

what happens when the recognition between sperm and egg triggers fusions of PM’s

A
  • sperm nucleus enters egg ( plasmogomy

- no more sperm should enter

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14
Q

fast block to polyspermy is triggered by

A

fusion of PM’s

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15
Q

w

A

11

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16
Q

seq fast block to polyspermy

A
  • unfertilized egg is polarized ( cytoplasm negatively charged relative to outside)
  • sperm PM fuses and nucleus enters egg -> ion channels in egg PM open
  • Na+ enter egg
  • egg membrane depolarizes
  • membrane depolarization prevents fusion with additional sperm
  • transient effect and last only ( 1 minute)
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17
Q

seq slow block to polyspermy

A
  • signal transduction pathway
  • binding of sperm to egg
  • release of Ca2+ from ER into cytoplasm of egg
  • triggers cortical granules
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18
Q

cortical granules

A

i. vesicles in cortex

ii. releases enzymes into space between PM & vitelline layer

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19
Q

Cortical Reaction is triggered by

A

by fusing of plasma membrane between sperm and egg

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20
Q

what happens during cortical reaction

A
  • Ca2+ released in egg from smooth ER
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21
Q

cortical granules

A
  • cortical granules fuse with plasma membrane ( vesicles containing enzymes that are stored below the plasma membranes)
  • enzymes relased ( into ZP) , trigger slow block to polyspermy
22
Q

mammal egg coverings

A

plasma membrane
zona pellucida
follicle cells

23
Q

in mammels fertilization reacts

A

internally

24
Q

acrosomal reaction in mammals

A
  • sperm binds to ZP3 ( glycoprotien in zona pellucida
  • binding triggers acrosome to burst ( releases enzymes, digests through pellucida)
  • no fast block to polyspermy
25
Q

cortical reaction in mammals

A
  • triggered by sperm binding
  • ca2+ released into cytoplasm
  • cortical granules release enzymes to outside of cell
  • enzymes
26
Q

enzymes in cortical reaction in mammals

A
  • catalyze hardening and alter sperm receptors of zona pelllucida
  • no additional sperm can bind
  • no fertilization envelope formed
27
Q

summary of fertilizations

A
  1. sperm has recognized egg
  2. sperm nucleus has entered egg
  3. changes to egg prevents polyspermy
28
Q

egg activation

A
  1. series of metabolic reaction in egg ( onset of embryonic development)
29
Q

what triggers egg activation

A

increased ca2+ in cytoplasm (cortical reaction)

30
Q

what are the changes in egg activation

A
  1. increased cellular respiration
  2. maternal enzymes and proteins activated
  3. increased proteins synthesis (maternal mRNA in cell)
31
Q

fusion of sperm and egg nuclei

A
  • same time as egg activation

- sperm nucleus guided to egg nucleus by microtubules

32
Q

egg development in sea urchins

A
  • eggs have completed meiosis when released from female
33
Q

egg development in humans

A
  • egg ( 2° oocyte) up to this point stalled at metaphase II , fertilizations triggers completion of meiosis
  • > sperm guided to egg nucleus
34
Q

female and male nuclei fuse

A

karyogamy

35
Q

when does sea urchin karyogamy

A

20 minutes after sperm nucleus enters egg

36
Q

how long does human karyogamy take

A

several hours

37
Q

zygote in egg development (karygomy)

A
  • 2n

- totipotent (potential to give rise to all cell types of new individual)

38
Q

end of fertilization

A

when zygote undergoes first division

39
Q

cleavage

A
  • series of rapid mitotic divisions with no growth,
40
Q

what is a result of cleavage

A

cell # increases, but cells get smaller & embryo size doesn’t increase
- results in blastomere

41
Q

cleavage furrow

A
  • indentation in cell surface as cytokinesis divides
42
Q

yolk

A
  • protien, phospholipids, fats -> food developing embryo

- amount varies among animal groups -> depends on needs of embryo

43
Q

stages of cleavege

A
  1. zygote ( one cell)
  2. embryo ( >= 2 cells )
  3. blastula ( >= 128 cells) - hollow ball, blastocoel
44
Q

echinoderms in mammals

A
  • very litle yolk
45
Q

equal holoblastic

A
  • uniform division across embryo
  • cleavage furrow passes entirely through egg causing blastomeres of equal size
  • blastocoel forms centrally
46
Q

assymetric yolk distribution

A
  • most yolk at vegetal pole of egg

- opposite end is animal pole

47
Q

unequal holoblastic cleavage

A
  • cleavage furrow passes entirely through egg, cytokinesis slowed down by yolk in vegetal hemisphere
48
Q

gray crescent

A
  • lighter color region
  • opposite site of sperm entry
  • gastrulation begins here
49
Q

continuation of division in frogs

A
  • yolk affects sizes of cells in two hemispheres
50
Q

animal hemispheres

A

blastomeres are smaller and more numerous

blastocoel forms entirely in animal hemisphere

51
Q

cleavge of birds

A
  • lots of yolk, cleavege furrow cannot pass through
52
Q

meroblastic cleavage

A
  • only region without yolk undergoes cleavage

bio (17 decks)

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