Mechanisms of gastrulation Flashcards

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1
Q

Animal half embryos give rise to…

A

animalised embryos.
Vegetal half embryos give rise to vegetalised embryos
This suggests embryos can change their development in response to environmental signals- developmental flexibility is associated with REGULATIVE DEVELOPMENT.

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2
Q

What is powerful micromeres?

A

An animal half embryo combined with 4 micromeres gives rise to a normal pluteus.

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3
Q

What is the archenteron?

A

It is formed from cells of the veg2 layer in intact embryos- not present in manipulated embryos.
THEREFORE MICROMERES ARE IMPORTANT REGULATORY INFLUENCE

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4
Q

How many micromeres are needed?

A

Animal 1 layer + 4 micromeres :normal pluteus
Animal 2 layer + 4 micromeres :vegetalised larva
Animal 2 layer + 2 micromeres :normal larva
Animal 2 layer + 1 micromere: animalised larva

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5
Q

Larva can be animalised or vegetalised by exposure to what?

A

Lithium ions - vegetalised

Zinc ions- animalised

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6
Q

The positional status may be defined in relation to what two gradients of influence

A

animalising gradient and vegetalising gradient

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7
Q
Lewis Wolpert (1960)
FRENCH FLAG MODEL
A

Each cell has potential to develop as red, white, blue.

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8
Q

B-catenin specifies..

A

Micromeres.
B-catenin is a transcription factor derived from maternal RNA deposited in the egg. Accumulates in micromere and veg2 cell nuclei,

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9
Q

What does B-catenin do?

A

.Stimulates expression of pmar1gene
.Switches off repressor
.Promotes development of endoderm, mesoderm and skeleton.

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