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Animal Developmental Biology > Developmental patterns in sea urchins > Flashcards

Developmental patterns in sea urchins Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Are sea urchins protostomes or deuterostomes?

A

Deuterostomes

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2
Q

What is karyokinesis?

A

Separation of genetic material

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3
Q

What are the 4 types of yolk distribution?

A

Isolecithal, mesolecithal, telolecithal, and centrolecithal

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4
Q

What is an isolecithal yolk distribution? What animals have it?

A

Evenly distributed yolk that is quite sparse. Found in echinoderms and mammals

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5
Q

What is an mesolecithal yolk distribution? What animals have it?

A

Moderate yolk distribution. Found in amphibians

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6
Q

What is an telolecithal yolk distribution? What animals have it?

A

Dense yolk throughout the cell. Found in fish and birds

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7
Q

What is an centrolecithal yolk distribution? What animals have it?

A

Yolk is clustered in the middle of the egg. Found in insects

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8
Q

What are the 2 cleavage types?

A

Holoblastic and meroblastic

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9
Q

What is holoblastic cleavage?

A

Complete cleavage, mitosis happens throughout cytoplasm, cytokinesis with each division. Found in echinoderms, mammals, and amphibians

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10
Q

What is meroblastic cleavage?

A

Incomplete cleavage, cytoplasm is split unevenly and cytokinesis doesn’t always occur. Found in fish, birds, and insects

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11
Q

Is the first mitotic division of a sea urchin egg meridional or equatorial? Which axis does the cell divide along? How many cells does the embryo end up with?

A

Meridional along animal-vegetal axis. 2 cells

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12
Q

Is the second mitotic division of a sea urchin egg meridional or equatorial? Which axis does the cell divide along? How many cells does the embryo end up with?

A

Meridional along animal-vegetal axis, perpendicular to division 1. 4 cells

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13
Q

Is the third mitotic division of a sea urchin egg meridional or equatorial? Which axis does the cell divide along? How many cells does the embryo end up with?

A

Equatorial, perpendicular to divisions 1 and 2. 8 cells

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14
Q

Is the fourth mitotic division of a sea urchin egg meridional or equatorial? Which axis does the cell divide along? How many cells does the embryo end up with?

A

The animal pole divides meridional and evenly into 8 mesomeres. The vegetal pole divides equatorial and unevenly into 4 macromeres and 4 micromeres. 16 cells total

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15
Q

What happens in the sixth mitotic division? How many cells does the embryo end up with?

A

Animal 1, animal 2, vegetal 1, and vegetal 2 layers form. End up with 60 cells because the small micromeres have stopped dividing

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16
Q

What happens to an embryo after the vegetal hemisphere, large micromeres, and small micromeres are removed?

A

It forms a Dauerblastula, an animal blastula, but won’t develop further because it is just ectoderm

17
Q

What happens to an embryo after the vegetal hemisphere, large micromeres, and small micromeres are removed. Then the large micromeres are reintroduced?

A

The animal cells organized themselves into a recognizable pluteus larva, and formed endoderm layers

18
Q

What is a logic circuit/gene regulatory network?

A

Gene product cascade that leads to induction, specification, and morphogenesis

19
Q

What is a feed forward circuit?

A

A gene product of an upstream gene enhances transcription/function of a gene product downstream

20
Q

What is a double negative circuit?

A

The gene product represses the function of a downstream product, which leads to an even more downstream product being activated because the gene product that was repressing it is no repressing it

21
Q

How are the large micromeres autonomously specified to become the organizers?

A

Dishevelled is localized at the vegetal pole, and it deactivates GSK3 so beta-catenin can enter the nucleus and act as a transcription factor. Other cells don’t have the localized Dishevelled, so the genes that get activated by beta catenin stay off in those cells

22
Q

What happens when embryos are treated with drugs to increase beta catenin activity?

A

It gets expressed in the vegetal 2 cells and not just the micromeres, which causes the digestive tract to develop outside the body

23
Q

What happens when embryos are treated with drugs to stop beta catenin activity?

A

Completely animalized blastula, same as the micromeres being removed

24
Q

What gene does beta catenin activate in the large micromeres?

A

Pmar1

25
Q

What does Pmar1 do?

A

Deactivates HesC

26
Q

What happens when HesC is deactivated?

A

Alx1 and Delta get expressed in the large micromeres

27
Q

How do Alx1 and Delta stay deactivated in any other cells that aren’t the large micromeres?

A

No beta catenin to turn on Pmar1, so HesC stays active and it represses Alx1 and Delta

28
Q

What does Delta do in the large micromeres?

A

It gets expressed on the surface of the micromeres, and interacts with Notch receptors on the Veg2 cells

29
Q

What does the Delta-Notch interaction cause the Veg2 cells to do?

A

Become non-skeletogenic mesenchyme cells that will direct gastrulation

30
Q

What do the large micromeres become for gastrulation?

A

Skeletogenic mesenchyme

31
Q

What happens to the skeletogenic mesenchyme cells right before gastrulation?

A

They undergo an EMT and ingress into the blastocoel

32
Q

What signals trigger the ingression of the skeletogenic mesenchyme into the blastocoel?

A

VEGF, FGF, beta catenin

33
Q

What do Snail and Alx1 do?

A

Promote endocytosis of the cell membrane with the adhesion molecules

34
Q

What cells deposit the spicules in the gastrula?

A

Skeletogenic mesenchyme

35
Q

Which cells trigger gastrulation?

A

The Veg2 cells: non-skeletogenic mesenchyme

36
Q

How does the blastopore form?

A

Invagination of the non skeletogenic mesenchyme

37
Q

What creates the force needed for the invagination that creates the blastopore?

A

Contraction of the actin filaments on the apical membrane of some non-skeletogenic mesenchyme epithelial cells

38
Q

What are the cells with the actin filaments on the apical membrane called?

A

Bottle cells

39
Q

What happens once the blastopore is formed?

A

The archenteron elongates inside, driven by non-skeletogenic mesenchyme cells grabbing on to the epithelial cells on the opposite side

Animal Developmental Biology (26 decks)

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