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BB10006 > Early mouse development > Flashcards

Early mouse development Flashcards

1
Q

What happens after the fertilisation of a mouse zygote?

A

The pronuclei fuse - one pronucleus contains the genetic material from the sperm and one pronucleus contains the genetic material from the ovum.

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2
Q

What happens after the pronuclei fusion?

A

The oocyte then divides to form two blastomeres which each contain identical genetic material.

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3
Q

How does the division of the fertilised cell occur?

A

It occurs by rotational cleavage - there can be an odd number of blastomeres at certain times.

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4
Q

What happens after the 8 cell stage?

A

Compaction occurs whereby the cells clump together surrounded by the zona pellucida.

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5
Q

What is the blastula called at the 16-cell stage?

A

A morula.

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6
Q

What happens to the morula?

A

The blastomeres will continue dividing and will eventually form a blastocyst.

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7
Q

What does a blastocyst consist of?

A

An inner cell mass surrounded by trophoblast cells, and contains a fluif-filled cavity called a blastocoele.

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8
Q

How does the blastocyst escape?

A

It escapes from the surrounding zona pellucida by secreting enzymes that digest a hole in the lining of the zona pellucida - this is called hatching.

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9
Q

What is the zona pellucida?

A

A protective incasement.

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10
Q

What is the trophoblast?

A

When the blastocyst forms it consists of two cell types - the inner cell mass and the trophoblast, the layer of cells around the outside.

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11
Q

What needs to happen after the blastocyst stage?

A

It needs to form a placental structure and be protected so it can carry on developing.

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12
Q

What is the “mouse version” of the uterus?

A

The two uterine horns.

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13
Q

Where will the embryos be implanted in?

A

Into the uterine horns.

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14
Q

What is the mouse version o the fallopian tube?

A

The oviduct.

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15
Q

What happens two the inner cell mass before implantation?

A

Two layers are formed - the epiblast and the hypoblast.

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16
Q

What forms the yolk sac cavity?

A

The primitive endoderm cells lining the blastocoel.

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17
Q

What forms the amniotic cavity?

A

The epiblast cells.

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18
Q

What will happen to the trophoblast cells that make contact with the uterine?

A

They will continue to divide and invade the uterus to form the syncytiotrophoblast.

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19
Q

What is gastrulation?

A

The formation of three cell layers - the ectoderm, endoderm and mesoderm. These layers are derived from the epiblast.

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20
Q

What is ingression?

A

When cells move internally underneath the rest of th epiblast layer.

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21
Q

What is the node?

A

A signalling region at a posterior position of the epiblast layer.

22
Q

How does the notochord form?

A

These are the cells that have moved through the node.

23
Q

What will the ectoderm cells form?

A

THe epidermis, brain, central nervous system.

24
Q

What will the mesoderm cells form?

A

Muscle, connective tissues, bone, kindey, gonads, tissues of the heart.

25
Q

What will the endoderm cells form?

A

Epithelium lining the gastrointestinal tract, epithelium lining the respiratory tract, liver, lung and pancreas.

26
Q

What is the embryo called after the three germ layers have formed?

A

Trilaminar embryo.

27
Q

What happens after gastrulation?

A

The ectodermal cells of the trilaminar start to thick and become the neural plate.

28
Q

What causes the formation of the neural plate?

A

Signalling from the underlying notochord.

29
Q

What happens after the neural plate is formed?

A

A neural groove forms along the midline of the neural plate and as the ectodermal cells continue to thicken, neural folds form either side of the groove. The folds rise and meet together to form the neural tube.

30
Q

What happens to the neural tube after formation?

A

It dissociates from the ectoderm and these cells are thought to become part of the endoderm. The other ectodermal cells form an overlying epithelial sheet and the neural tube will eventually form the spinal cord and brain.

31
Q

Give the basic outline of mammalian early development.

A

There is rotational cleavage in the embryo and a blasocyst forms prior to implantation. The inner cell mass organises into the epiblast and the primitive endoderm. Gastrulation occurs to form the three germ layers, neurulation forms the neural tube and the germ layers will eventually give rise to all the tissues and organs due to organogenesis.

32
Q

What is lineage restriction?

A

The idea that a cell will only give rise to certain cell types depending on its position.

33
Q

Why wouldn’t you use genetic screens for mice?

A

They have too large of a genome, a longer generation time, it’s expensive and the adults are bigger.

34
Q

Why might you want to express a gene in mouse?

A

If you think a gene influences development, you can see the effect of it when it’s in the mouse.

35
Q

How can a gene be put into a mouse?

A

Use a plasmid (with RE, ligation etc) and put your gene in. Inject the liquid containing the DNA into the mouse eggs using a holding pipette. The DNA should be injected into the male pronuclei as it is larger. The zygotes then need to be transferred to a surrogate parent.

36
Q

What is an easy identification method for transgenic mice?

A

GFP expression in the epidermis.

37
Q

Why do most transgenic mice need to be screened by PCR?

A

As the GFP may not be expressed in their epidermis so will not be seen.

38
Q

How does the method for overexpressing a gene product in the Xenopus differ?

A

You can inject mRNA into the frogs instead of DNA - but this is not stably introduced and the mRNA will degrade so the effect will not last.

39
Q

What does chimeric mean?

A

An organism that contains at least 2 sets of DNA.

40
Q

How can you create targeted knockout mice?

A

Obtain embryonic stem cells, make a targeting vector, genetically modify the cells, inject the cells into blastocyst embryos, implant the recombinant embryos into a surrogate mother and breed the pups.

41
Q

How can you obtain embryonic stem cells for targeted knockout genetics?

A

Take them from the inner cell mass.

42
Q

What is the trophectoderm?

A

The placenta.

43
Q

What is a targeting vector/construct?

A

It is made up of pieces of DNA stitched together using molecular biology techniques. It can
be purified from the bacterial plasmid and used within and ES to cause a genetic deletion.

44
Q

What happens after the targeting construct is added to embryonic stem cells?

A

The DNA construct moves into the nucleus where homologous recombination occurs.

45
Q

How can you see if the targeting construct was successful?

A

Use a selectable marker such as neomycin. A resistance gene in the targeting construct can be used to see this. You could also use a reporter gene such as a colour.

46
Q

What is the other method for getting ES into a mouse?

A

Micro-injection into the host blastocyst.

47
Q

When transferring to a surrogate mother, where do they need to be placed?

A

One of the uterine horns.

48
Q

What is Pdx1?

A

A transcription factor that affects the pancreas development.

49
Q

What is the difference between reverse genetics and forward genetics?

A

Reverse genetics starts with a gene that you want to investigate and forward genetics starts with a random mutation and aims to find the gene.

50
Q

Classify mouse knockout and genetic screen as forward and reverse genetics.

A

Mouse is reverse, genetic screen is forward.

BB10006 (24 decks)

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