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Animal Developmental Biology > Mammals > Flashcards

Mammals Flashcards

1
Q

Why is it difficult to study development in mammals?

A

Completely internal

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2
Q

Where does fertilization occur?

A

Oviduct

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3
Q

Where do the early stages of development occur?

A

Fallopian tubes

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4
Q

What type of yolk distribution is seen in mammals?

A

Isolecithal

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5
Q

What type of cleavage is seen in mammals?

A

Holoblastic, rotational

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6
Q

How does a morula become a blastocyst?

A

Compaction of cells

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7
Q

How does compaction occur to form a blastocyst?

A

Changes in cell adhesion through E-caderins, which increase the contact area between cells and causes really tight packing, and from cytoskeletal rearrangements

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8
Q

What are the two cell types in a blastocyst?

A

Trophoblast and ICM

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9
Q

At what cell stage do the trophoblast and ICM become specified?

A

32 cells

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10
Q

What are the 2 transcription factors that specify if a cell will become part of the trophoblast or part of the ICM?

A

Oct4 and Cdx2

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11
Q

What does the trophoblast become?

A

Extra-embryonic tissue. It becomes the chorion

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12
Q

What does the ICM become?

A

The embryo and the amnion

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13
Q

Which transcription factor specifies trophoblast?

A

Cdx2

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14
Q

Which transcription factor specifies ICM?

A

Oct4

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15
Q

What does Cdx2 do?

A

Inhibits Oct4 to specify cells to become trophoblast cells

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16
Q

What does Oct4 do?

A

Inhibits Cdx2 and turns on Sox2 to specify ICM cells

17
Q

What does Sox2 do?

A

Promotes its own activity and the activity of Oct4. Turns on Nanog transcription

18
Q

What does Nanog do?

A

Promotes activity of Oct4, Sox2 and itself

19
Q

How does implantation of the blastocyst in the uterus occur?

A

Cell adhesion. First through labile interactions then through permanent interactions

20
Q

What creates the labile interactions that lead to implantation?

A

Sulfated polysaccharides on the endometrium bind to L-secretin on the blastocyst

21
Q

What creates the permanent interactions that lead to implantation?

A

P-cadherin is expressed by both the blastocyst and the endometrium

22
Q

What cell movement splits the ICM into 2 layers?

A

Delamination

23
Q

What are the 2 layers formed when the ICM splits into 2 layers? What do they become?

A

Hypoblast forms the yolk sac and epiblast forms the amnion and embryo

24
Q

In mammals, the positioning of the germ layers and the cell movements are very similar to which animal?

A

Chickens

25
Q

Which germ layer ends up in the original place of the hypoblast?

A

Endoderm

26
Q

Which germ layer ends up in the original place of the epiblast?

A

Ectoderm

27
Q

What are the 2 cell layers that make up the placenta?

A

Cytotrophoblast and syncytiotrophoblast

28
Q

What is the cytotrophoblast?

A

A single layer of cells around the embryo

29
Q

What is the syncytiotrophoblast?

A

A large network of cytoplasm that forms extracellular spaces in the growing tissue

30
Q

How is the umbilical chord formed?

A

Differentiation of fetal blood vessels that connect with the mother’s vessels in the placenta

31
Q

What are the 3 types of twins?

A

Monozygotic, dizygotic, conjoined

32
Q

How genetically similar are identical twins?

A

Identical genetic makeup

33
Q

How many amnions and chorions would be created for a set of monozygotic twins that had the zygote split very early on?

A

2 amnions and 2 chorions. Early splits form two blastocysts that both implant and each one has tissues specified into trophoblast and ICM

34
Q

How many amnions and chorions would be created for a set of monozygotic twins that had the ICM split?

A

Two amnions and 1 chorion. The trophoblast and ICM are already specified, so each embryo still has its own amnion but they share trophoblast tissue

35
Q

How many amnions and chorions would be created for a set of monozygotic twins that had the zygote split very late?

A

1 amnion and 1 chorion. The embryo would have split after some of the ICM branched off into the amnion, so the embryos share an amnion

36
Q

How do dizygotic twins occur? How genetically similar are they?

A

Two eggs get ovulated and they both get fertilized and implanted. They are no more similar to each other than regular siblings

37
Q

What are conjoined twins?

A

Twins that share some organs and tissues

38
Q

What are 3 possible causes for conjoined twins?

A
  1. A second organizer is created and creates a new body axis
  2. Trauma that splits the epiblast
  3. Confused Nodal

Animal Developmental Biology (26 decks)

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