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Life Processes > Animal development > Flashcards

Animal development Flashcards

1
Q

Fertilisation

A

Internal or external

Activates egg - meiotic division -reinitiates transcription and translation - prevent polyspermy

Establishes pattern - point of fertilisation - defines plane of first cell division in amphibians - nematodes - anterior pole

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2
Q

Process of fertilisation

A

Sperm makes contact with egg and discharges contents of acrosome by exocytosis

Hydrolytic enzymes released to penetrate eggs jelly coat

Plasma membrane of egg and sperm fuse - sperm contents enter cytoplasm

Polyspermy has to be prevented - fast and slow block

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3
Q

Fast block to polyspermy

A

A neuron-like electrical response (depolarisation) of the egg plasma membrane

This prevents a second sperm from fusing with the membrane - 2 second timescale

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4
Q

Slow block to polyspermy

A

Cortical reaction

After membrane fusion - cortical granules fuse with the egg’s plasma membrane - releasing their contents

Enzymes separate the plasma and vitelline membranes

Mucopolysaccarides cause water (by osmosis) to enter the peri-vitelline space - physical separation of two membranes - contents harden

Vitelline membrane known as the fertilisation membrane

20 seconds

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5
Q

Cleavage

A

Rapid mitotic divisions

1-2-4-8-16

divide fertilised egg into nucleated blastomeres

No increase in embryo size

32 cell stage called a morula

Hollow ball of blastomeres - blasatula - cavity - blastocoel

Controlled by maternal proteins and RNAs

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6
Q

Gastrulation

A

Cell and tissue movements rearranging the blastula

Establishes multilayered body plan

Cells that will form endodermal and mesodermal tissue move inside the embryo - ectoderm remains external

Varies between species but has a common core process

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7
Q

Gastrula

A

two cell layer thick hollow embryo

Created by invagination of cells with endoderm fate

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8
Q

Blastopore

A

Point of invagination in gastrulation

Protostomes - forms mouth first - annelids, molluscs, arthropods

Deuterostomes - forms anus first - echinoderms, chordates

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9
Q

Blastocoel

A

Cavity of blastula

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10
Q

Archenteron

A

Interior space of gastrula

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11
Q

Endoderm

A

Forms gut and associated organs

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12
Q

Ectoderm

A

Forms epidermis and central nervous system

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13
Q

Mesoderm

A

Forms muscle

Forms from pouches of cells that pinch off from the endoderm

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14
Q

Diploblastic

A

2 tissue layers - ecto and endoderm

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15
Q

Triploblastic

A

3 tissue layers - ecto, meso and endoderm

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16
Q

Chicken gastrulation

A

occurs on small plate of tissue on a huge yoke

Only cells on top of the yolk cleave

The morula is a disk of cells on the yolk - blastodisc

Gastrulation occurs by separation of upper ectoderm from lower endoderm and not invagination

Mesoderm tissue forms by invagination of cells in line of ectoderm

17
Q

Mammalian gastrulation

A

Blastocyst is rougly 100 cell hollow ball containing inner cell mass

Inner cell mass surrounded by trophoblast

endoderm forms from lower side of inner cell mass

Ectoderm forms from upper cell mass

Mesoderm froms by invagination of upper ectoderm

18
Q

Protostomes

A

Mouth forms first from point of invagination

Spiral cleavage - diagonal to vertical axis

Determinate cleavage - fate set early

19
Q

Deuterostomes

A

Anus forms first from point of invagination

Radial cleavage - parallel to vertical axis

Indeterminate cleavage - fate set late

20
Q

Neurulation

A

Notochord:

Feature of all chordates

Longitudinal flexible rod between gut and nerve cord

Longitudinal skeletal support

Not the vertebral column

Nueral tube:

Nervous system

Forms from plate of dorsal ectoderm:

Neural plate

Neural groove

Neural crest

21
Q

Neural crest

A

Anteriorly forms the brain and parts of sensory organs

Posteriorly it will form other structures - including ganglia

22
Q

Notocord

A

mesodermal origin

23
Q

Embryo maintenance in birds

A

Aqueous environment - egg

Extra embryonic membranes are formed from the blastodisc:

The yolk sac

The amnion

The chorion

The allantois

As embryo develops - pinches itself off from these membranes - remains attached to the yolk at mid body position

24
Q

Embryo maintenance in mammals

A

Amnion - space above ectoderm

Chorion develops from trophoblast

Allantois - out pocket of embryo gut - later incorporated into umbilical cord

25
Q

Invagination

A

Invagination occurs during gastrulation and neurulation

Occurs from changes in shape of cells - caused by action of microtubules and actin filaments

Wedge shaped cells cause tissue invagination

26
Q

Cell and tissue movement

A

Movement of cell position - change of shape of tissues and embryos

Use cytoskeleton to change position - extends the cell and the cell ‘crawls’

Undergo convergent-extension and change tissue and embryo shape

27
Q

Cell-cell adhesion

A

key to embryo development and tissue formation

Controlled by the extra-cellular matrix (ECM) - mixture of secreted glycoproteins - guide cells

Helps to hold cells together when they reach their final place

Different molecules allow different cellular interactions/adhesions

28
Q

Fate maps

A

What part of embryo develops into what part of the animal

Tissue can not be differentiated into the tissue it is fated to be but still has the fate to become that tissue

C. Elegans - nematode - fully mapped - ends up with same 959 cells

29
Q

Stem cells and embryonic stem cells

A

Stem cells are totipotent

As development continues totipotency decreases

Adult stem cells have varying pleuripotency - can develop into a range but not all cells

Embryonic stem cells are completely totipotent

30
Q

The control of fate

A

Developing cells acquire fate

Fate determination - gene expression

differentiation by tissue specific gene expression

Chromatin affects gene expression

31
Q

Cytoplasmic determinants

A

Control gene expression

generate first differences in embryos

Maternally provided

32
Q

Cell-cell induction

A

Cells of the embryo signal to one another

induce same fate in neighbouring cells

Cell-cell signals may be molecules attached to the cell membrane or may be locally diffusing molecules

33
Q

Maternal effect genes in Drosophila

A

Cytoplasmic determinants in unfertilized eggs

Maternal effect genes

Bicoid:

Anterior concentration of mRNA

at fertilisation - translated to protein

Diffuse through embryo

Morphogen gradient

Injection of bicoid protein into bicoid mutant will reestablish anterior pole

Life Processes (9 decks)

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