Development I Flashcards Preview

Biology 116 > Development I > Flashcards

Flashcards in Development I Deck (45):
1

development

-all the changes in life cycle
-includes embryonic developmental birth/hatching, metamorphosis, etc

2

model organisms

species chosen for research -> easily studied

3

what are the consequences of fertilization?

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

4

external egg structure

plasma membrane with 1+ coverings
-aid in fertilization
-barrier to interspecific fertilization (especially important for species/external fertilization)

5

steps in fertilization

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

6

why are echinoderms used in research a lot?

-readily available
-easy to work with
-easy to obtain lots of gametes
-external fertilization - easy to observe

7

name the egg coverings of sea urchins external to internal

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

8

what are the steps in sea urchin fertilization?

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

9

describe the external fertilization in sea urchins

-gametes released into water
-egg jelly coat releases chemicals -> attract sperm (chemotaxes)

10

acrosomal reaction (sea urchins)

-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

11

preventing polyspermy (sea urchins)

-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)

12

fast block to polyspermy (sea urchins)

-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

13

cortical reaction/slow block to polyspermy (sea urchins)

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

14

name the egg coverings of mammals outside to inside

PM -> zona pellucida -> follicle cells

15

what are the steps in mammal fertilization

1. acrosomal reaction
2. cortical reaction/slow block to polyspermy

16

fast block to polyspermy in mammals

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

17

where are eggs fertilized in mammals?

internally - inside oviduct

18

acrosomal reaction (mammals)

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

19

cortical reaction/slow block (mammals)

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

20

describe the fertilization envelope in mammals

TRICK QUESTION. THERE IS NO FERTILIZATION ENVELOPE IN MAMMALS

21

egg activation

-triggered by sperm binding
-series of metabolic reactions starts, accelerate (onset of embryonic development)

22

what are the results of egg activation?

-increase respiration
-maternal enzymes and proteins activated
-increase protein synthesis - mRNA already present

23

what is the 2° oocyte triggered by?

sperm binding

24

for humans, when does the 2° oocyte arrest?

metaphase II

25

what triggers continuation? what happens as a result?

fertilization. meiosis is complete

26

when do sea urchin eggs complete meiosis?

before release

27

karyogamy

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

28

totipotent

potential to give rise to all cell types

29

end of fertilization

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

30

compare and contrast fertilization in sea urchins and mammals

sea urchins
-echinoderms - in ocean
-external fertilization
-fast and slow blocks
-fertilization envelope

mammals
-aminotes
-internal fertilization
-slow block only
-no fertilization envelope

31

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

cleavage. single celled zygote becomes a MC embryo

32

characteristics of cleavage

-rapid mitosis
-very short/no G1 or G2 Phases
-no cell growth

33

what are the stages of cleavage?

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

* at least 128 blastomeres cells of the blastula

34

deuterostomes

radial and indeterminate

35

yolk

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

36

animal pole

where embryo is

37

vegetal pole

where yolk is

38

cleavage furrow

indentation during cytokinesis

39

how does yolk affect the pattern of division?

amount and distribution of yolk varies between animal groups
-little yolk -> faster, equal cleavage
-lots of yolk -> slower, unequal cleavage

40

equal holoblastic

-cleavage furrow passes entirely through egg
-equal division of egg cytoplasm -> equal blastomeres

41

unequal holoblastic

-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

in what species does unequal holoblastic occur?

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

43

meroblastic cleavage

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

44

in what species does equal holoblastic occur?

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

45

in what species does meroblastic cleavage occur?

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