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zygote neurula Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Name stages of early embryogenesis

A
  1. zygote
  2. cleavage (mitosis)
  3. morula
  4. blastula (first embryonic cavity)
  5. gastrulation (forms germ layers)
  6. gastrula (new cavity)
  7. organogenesis (neurulation, forms chorda dorsalis, then systems + organs) (vertebrates)
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2
Q

what kind of cells made during cleavage

A

during cleavage, volume of egg cytoplasm is divided into smaller cells called BLASTOMERES

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3
Q

what triggers blastomere division. (cleavage)
what is the role of cylin dependant kinases

A

. activation of mitosis promoting factor (MPF) which is a type of CDK
. regulates the cell cycle of early blastomeres

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4
Q

what does initial activation of MPF do

A

causes alternating M + S phases, no gap phases (G1+G2)

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5
Q

is yolk concentration high in the animal pole?
what is yolk rich pole known as

A

. quite low. cellular divisions faster at animal pole
. vegetal pole

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6
Q

what is the purpose of the blastula

A

. provides first cell layer + cavity (blastocoel) in embryo

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7
Q

what is a blastoderm

A

the wall of the blastula formed from blastomeres

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8
Q

role of blastocoel

A

. provides space for gastrulation cell movements
. prevents premature interactions btw cells with different future development

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9
Q

what determines the look of the blastula

A

pattern of yolk distribution + gradient of some molecules in ooplasm

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10
Q

brief expl blastula formation in mammals

A

. first 2 days, division of cells = 24 hours
. division of mammalian blastomeres = asynchronous (dont happen at same time)
. embryo 16 cells = morula
. in mammals the blastula is called BLASTOCYST

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11
Q

why after blastocoel formation in mammals its called blastocyst not blastula

A

blastula - all of it is part if the embryo
in mammlas, only some cells form embryo, others form foetal part of placenta + envelopes?

Blastocyst is what implants into uterus
It also has other struxtures like trophoblasts

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12
Q

types of cell movement during gastrulation

A

.Invagination - epithelial cells bends inwards
.Ingression - individual cells leave epithelial sheet + become migrating mesenchyme cells
.Involution - epithelial sheet rolls inward + forms underlying layer
.Epiboly - sheet of cells spread by thinning
.Delamination - one cell layer migrates + develops second layer.

** pg 10 look ppt for pics :)

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13
Q

explain diploblastic + triploblastic animals

A

Diploblastic (radiata) - forms ecto and endoderm
Triploblastic (animals with bilateral body symmetry) - ecto, meso, endoderm

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14
Q

protostomes vs deuterostomes

A

P. mouth then anus, coelom forms from splitting of mesoderm.

D. anus then mouth, coelom forms from mesodermal budding of archenteron (cavity wth 2 openings)

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15
Q

what does the neural tube + crest do

A

gives rise to spinal cord + brain
neural crest cells migrate form tube + forms different cells

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16
Q

Neuralation brief expl

A

*cuboidal cells turn columnar, = thickens ectoderm
*cell adhesion causes edges of the plate fold+ rise to form a tube
*cells at tips of neural folds become neural crest cells (epidermis + n plate can give rise to this)
*somites form pairs flanking neural tube + form segmental pattern in vertebrate embryo

17
Q

explain mosaic development

A

. fertilised ovum undergoes determinate cleavage
. each blastomere has limited development potency
. blastomere is precursor of specific part of embryo.
. blastomere damage/detruction = defective organism
. this due to ooplasmic segregation of morphogens
* not valid for mammalian eggs

18
Q

what are morphogens

A

. they direst cell/tissue development
. theyre conc gradients in oocytes = ooplasmic segregation
. blasmomeres get a specific set of them during cleavage
. in early devlpmnt the gradients cause diff cells types in distinct spatial order
.*they act by inducing/maintaining expression of diff tagrget genes
* M are secreted proteins that signal btw cells, TF or small molecules

19
Q

when does ooplasmic segregation finish and what happens next

A

after sperm egg contact.. provokes movement cortical ooplasm
first cleavage furrow goes through middle of grey crescent therefore first 2 blastomeres equal.
next divisions, blastomeres takes diff cytoplasm (depends on location)
* final ooplasmic segregation forms ant/post + ventral/dorsal axis of symmetry

20
Q

what are presumptive regions

A

cell groups predetermined for certain cell fate (before differention). determinations of these regions increase during early gastrulation

21
Q

why can amphibian embryos be used to revel things in early embryogenesis

A

they develop in water so can be experimented at all stages. jelly coat can be removed and microsurgeries easily performed on the eggs so no complicated/expensive tools needed

22
Q

stages of the amphibian embryo

A
  1. first cleavage divides zygote into 2 equal blastomeres ( each takes half whats needed morphogens in correct gradient)
  • if first 2 blastomeres split, they’ll become 2 genetically identical normal larvae
  • if grey crescent stays in only 1 of them, only that blast becomes normal larva
23
Q

how do you get conjoined twins (gastrula)

A

if you split the presumptive region into 2, you create 2 organizers in same embryo: 2 sets of neural tubes + notochord created.

24
Q

Why do mammals not need egg yolk

A

Bc They have placenta

Birds and frogs need lots of yolk since their eggs develop outside body

25
Q

Do fish or amphibians have more yolk?

A

Fish has more yolk bc they have no larval stage-no metapmorphasis (when egg hatches tiny fish comes out no tadpole etc)

26
Q

What is the result of yolk being evenly distributed in mammals

A

Mammalian cleavage complete and blastomeres equal size

27
Q

How is a frogs have asymmetrical blastomeres

A

3rd cleavage furrow =equatorial cleavage delayed in vegetal part of the egg

28
Q

What is the grey crescent

A

Is a structure of AMPHIBIANS that determines body symmetry

29
Q

How is grey crescent formed in external fertilization of amphibians

A
  • Sperm has to penetrate animal pole as vegetal pole full of yolk
  • Sperm carries centrioles which contains microtubules to allow rotation of cortical layer of egg
  • Mixes dark and light cytoplasm= grey crescent

Grey crescent is the future dorsal part of embryo, notochord formed. When crescent bisected-we get left+right

30
Q

What chromosomes produce molecules for early embryonic development of amphibian

A

Lampbrush chromosomes (found in oocytes of animals except mammals)

Biology (36 decks)

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