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Biology 116 > Development I > Flashcards

Development I Flashcards

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1
Q

development

A
  • all the changes in life cycle

- includes embryonic developmental birth/hatching, metamorphosis, etc

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2
Q

model organisms

A

species chosen for research -> easily studied

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3
Q

what are the consequences of fertilization?

A
  • restores diploid number
  • determines sex (sometimes)
  • sperm content activates egg -> start development
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4
Q

external egg structure

A

plasma membrane with 1+ coverings

  • aid in fertilization
  • barrier to interspecific fertilization (especially important for species/external fertilization)
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5
Q

steps in fertilization

A
  1. sperm dissolves protective layers around egg
  2. sperm binds to egg surface receptors - ensure same species
  3. change to egg surface - prevent polyspermy
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6
Q

why are echinoderms used in research a lot?

A
  • readily available
  • easy to work with
  • easy to obtain lots of gametes
  • external fertilization - easy to observe
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7
Q

name the egg coverings of sea urchins external to internal

A

jelly coat -> sperm-binding receptors -> vitelline layer -> egg PM

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8
Q

what are the steps in sea urchin fertilization?

A
  1. Ascosomal reaction
  2. fast block to polyspermy
  3. cortical reaction - slow block to polyspermy
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9
Q

describe the external fertilization in sea urchins

A
  • gametes released into water

- egg jelly coat releases chemicals -> attract sperm (chemotaxes)

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10
Q

acrosomal reaction (sea urchins)

A
  • acrosome in sperm head releases hydrolytic enzymes -> break down jelly coat
  • acrosomal process/filaments bind sperm-binding receptor
  • recognition triggers plasmogamy - sperm and egg PMs fuse -> sperm nucleus enters egg
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11
Q

preventing polyspermy (sea urchins)

A
  • more than 1 sperm nucleus enters egg (more fatal - abnormal chromosome #)
  • 2 mechanisms to ensure only 1 sperm enters (fast block ~ 1-3 sec, slow block ~ 1 min)
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12
Q

fast block to polyspermy (sea urchins)

A
  • seconds after membrane fusion: ion channels open in egg PM -> electric “zap” that repels other sperm on egg surface -> prevents addition sperm/egg PM fusion
  • lasts ~ 1 min
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13
Q

cortical reaction/slow block to polyspermy (sea urchins)

A
  • also triggered by plasmogamy (membrane fusion)
  • vitelline layer separates, hardens -> fertilization envelope-protective layer -> complete block - irreversible, permanent
  • requires ~ 1 minute
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14
Q

name the egg coverings of mammals outside to inside

A

PM -> zona pellucida -> follicle cells

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15
Q

what are the steps in mammal fertilization

A
  1. acrosomal reaction

2. cortical reaction/slow block to polyspermy

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16
Q

fast block to polyspermy in mammals

A

TRICK QUESTION! THERE IS NO FAST BLOCK TO POLYSPERMY IN MAMMALS

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17
Q

where are eggs fertilized in mammals?

A

internally - inside oviduct

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18
Q

acrosomal reaction (mammals)

A
  • sperm binds receptor in zona pellucida

- acrosome bursts and release enzyme (helps sperm get through zona pellucida)

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19
Q

cortical reaction/slow block (mammals)

A

-enzymes catalyze changes in zona pellucida -> ZP hardens -> filters sperm receptors so that no sperm can bind

20
Q

describe the fertilization envelope in mammals

A

TRICK QUESTION. THERE IS NO FERTILIZATION ENVELOPE IN MAMMALS

21
Q

egg activation

A
  • triggered by sperm binding

- series of metabolic reactions starts, accelerate (onset of embryonic development)

22
Q

what are the results of egg activation?

A
  • increase respiration
  • maternal enzymes and proteins activated
  • increase protein synthesis - mRNA already present
23
Q

what is the 2° oocyte triggered by?

A

sperm binding

24
Q

for humans, when does the 2° oocyte arrest?

A

metaphase II

25
Q

what triggers continuation? what happens as a result?

A

fertilization. meiosis is complete

26
Q

when do sea urchin eggs complete meiosis?

A

before release

27
Q

karyogamy

A
  • microtubules guide sperm nucleus to egg
  • sea urchins ~ 20 minutes after sperm nucleus enters
  • humans - several hours
  • results in diploid, totipotent zygote
28
Q

totipotent

A

potential to give rise to all cell types

29
Q

end of fertilization

A
  • when zygote undergoes first division -> embryo
  • sea urchins - within 90 minutes
  • mammals - 12-26 hours
30
Q

compare and contrast fertilization in sea urchins and mammals

A

sea urchins

  • echinoderms - in ocean
  • external fertilization
  • fast and slow blocks
  • fertilization envelope

mammals

  • aminotes
  • internal fertilization
  • slow block only
  • no fertilization envelope
31
Q

what is the second step in embryonic development and what is formed as a result?

A

cleavage. single celled zygote becomes a MC embryo

32
Q

characteristics of cleavage

A
  • rapid mitosis
  • very short/no G1 or G2 Phases
  • no cell growth
33
Q

what are the stages of cleavage?

A

zygote (1 cell) -> 24 hours -> embryo (2 + cells) -> blastula: hallow (blastocoel inside = nothing)*

  • at least 128 blastomeres cells of the blastula
34
Q

deuterostomes

A

radial and indeterminate

35
Q

yolk

A

mixture of proteins, phospholipids, fats -> food for developing embryo (like endosperm - convergent evolution)

36
Q

animal pole

A

where embryo is

37
Q

vegetal pole

A

where yolk is

38
Q

cleavage furrow

A

indentation during cytokinesis

39
Q

how does yolk affect the pattern of division?

A

amount and distribution of yolk varies between animal groups

  • little yolk -> faster, equal cleavage
  • lots of yolk -> slower, unequal cleavage
40
Q

equal holoblastic

A
  • cleavage furrow passes entirely through egg

- equal division of egg cytoplasm -> equal blastomeres

41
Q

unequal holoblastic

A
  • cleavage furrow passes entirely through egg
  • yolk slows down cytokinesis in vegetal pore -> unequal divisions of egg cytoplasm -> unequal blastomeres (more/smaller blastomeres in vegetal pole, fewer larger blastomeres in vegetal pole)
42
Q

in what species does unequal holoblastic occur?

A

species with medium amount of yolk - e.g. amphibians

43
Q

meroblastic cleavage

A

cleavage furrow does NOT pass entirely through egg (ONLY through pole)

44
Q

in what species does equal holoblastic occur?

A

occurs in species with little yolk (e.g. sea urchins, humans)

45
Q

in what species does meroblastic cleavage occur?

A

occurs in species with a LOT of yolk - birds, other reptiles, fish

Biology 116 (19 decks)

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