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Cells To Organisms > Signalling > Flashcards

Signalling Flashcards

1
Q

What is cell signalling capacity?

A

Ability of an organism to send/receive signals. Quantified by counting the number of signalling proteins an organism has.

Multiicellular organisms devote x10 genes to signalling

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2
Q

What is long range signalling?

A

Endocrine signalling, range is up to 1000 mm. Hormones travel in blood between brain and organs.

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3
Q

Examples of long range signalling humans:

A

Eg Sexual dimorphism. Hypothalmus secretes GnRH-> anterior pituitary secretes GH-> stimulates secretion of LH and FSH-> gonads -> sex steroids/inhibin
Sex steroids/inhibin STOP Hypothalmus and STOP anterior pituitary

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4
Q

Examples of long range signalling plants:

A

Flowering in Arabidopsis: CO production stimulated by light, and accumulates when days are long. High CO promotes FT synthesis. FT moves to the shoot and starts flower production.

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5
Q

What is competence?

A

The ability of a cell or tissue to respond to a signal (ie have receptor for that signal)

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6
Q

Are nerves long range?

A

The brain to muscles is long range but it is done through short range signalling (axon to synapse)

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7
Q

What can be signals?

A

-Proteins
-small hydrophobic/hydrophillic molecules
-gas
-electrical impulses

proteins (insulin, FGF)
small hydrophobic (steroid hormones)
small hyrdophilic (plant auxins)
gas (ethylene, NO)
electrical (nerve impulses)

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8
Q

How do neurons signal?

A

Signal moves along axon and trasmitted to the synapse, the pre-synaptic cell releases NT and goes across synapse and binds receptors on post synaptic cell which triggers further nerve impulses

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9
Q

How is male sex determined in humans?

What structures are changed? What hormones?

A

Determined at fertilization. If you have Y chromosome then testosterone signals to develop gonads and during puberty 2ndry sex characteristics. Testosterone signals male Wolfian duct to become Vans deferens and activate mullarian-inhibiting substance. Testosterone is a steroid hormone.

Vans deferens carries sperm.

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10
Q

How is female sex determined in humans?

A

Born with XX, then there are no signals stopping Mulliarian duct from becoming the oviduct and no signals telling Wolfian duct not to die (so it does). Female is the default.

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11
Q

What is CAIS?

complete androgen insensitivty syndrome

A

lack of androgen receptors in XY. Has internal testes (but never develop) and develops female characteristics at puberty. Evidence that female is the default bc need androgen competence to develop male.

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12
Q

How is testosterone produced?

A
  1. genetic signal instructing gonad development
  2. If gonads are XY they secrete a TF (Sry) which stimulates testes differentiation
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13
Q

How is sex determined in chickens?

A

Cell autonomus sex determination. Male=ZZ (wattle, gold, spur) female=ZY (no wattle or spur, brown) Sex is determined due to genetic signal. Starts off as sex netural then goes to sex specific development like humans. Long range signalling is NOT the primary component in driving sexual dimorphism

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14
Q

Whats a gyandromorph?

A

Half female+male. Mix of ZZ and ZW cells. In chickens: shows endocrine signalling not sufficent to produce 2ndry sex characteristics and proves ZZ and ZW cells have intrinsic sex identity.

Humans do not have cell autonomey which is why this cant happen

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15
Q

Whats a mosaic?

A

Genetic change in cell lineage from a single zygote

Fertilization occured, happens in one embryo where one cell changes

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16
Q

What is a chimera?

A

Fusion of genetically distinct embryo

Two different embryo come together

17
Q

How is sex determined in aligators?

And in fish and turtles

A

TSD, growing concern as climate change gets worse especially with fish.

Temeperature dependent sex determination

18
Q

What is intermediate range signalling?

A

Paracrine signalling, range of 0.01-1mm.

19
Q

Example of intermediate range signalling:

A

Pentadactyl limb formation (conserved between tetrapods)

ie mice humans chickens

20
Q

How are limbs formed?

A

Starts shortly after fertilization and limbs are so small that paracrine signalling is sufficent.
1. patterning when limb is small
2. growth to reach final size
3. mediated by paracrine signalling

Limb bud has 3 axes which drives differentiation between limb compartments into mature limbs

21
Q

What role does the proximo distal axis have in limb formation?

base to tip

ie shoulder (proximo) finger tip (distal)

A

The AER is at the tip of limb bud, and the earlier you remove the AER the less formation you have along the proximo-distal axis

22
Q

What is the relationship between AER and FGF4

A

AER can be replaced with FGF4 (signalling molecule). A soaked FGF4 bead was sufficent to induce proximo-distal axis formation.

Ectopic exrpression of FGF4 is why daushaunds have stumpy legs

23
Q

What role does the anterior posterior axis have in limb formation?

A

ZPA is at the posterior edge. If you graft ZPA onto anterior edge you get mirror wing formation.

Zone polarizing activity

24
Q

Explain the french flag model

A

The level of morphogens dictates pattern formation. Thought that specific range of morphogen conc specifies each digit (true).

French flag make like triangle and then the boxes inside the triangle

25
Q

How is Shh related to ZPA?

A

Shh is the morphogen that ZPA secretes. If you put Shh cells on the anterior edge of limb bud, mirror wing forms. Means Shh is sufficient.

26
Q

What is an organizer?

A

Signalling center that directs development of whole embryo or part of it. Eg ZPA

27
Q

What is short range signalling?

A

Juxtacrine. Less than 0.01 mm. Cell-cell contact signalling

28
Q

Examples of short range signalling in plants

A

Trichomes. They differentiate from epidermal precursor cell. Each epidermal cell decides whether to develop into a trichome depending on juxtacrine signalling- no randomness but spacing variation & density cld be changed with signal. Non-autonomus.

Trichomes never touch

29
Q

What is lateral inhibition?

A

Cell inhibits cells touching them from adopting the same fate. Eg trichome formation, eg sensory bristles in drosophilia, eg trees spaced out in woods

30
Q

Examples of short range signalling in animals:

A

Grasshoppers/drosophilia: sensory bristles are each connected to a neuron, each form in center of cells. Example of lateral inhibition.

31
Q

What is contact repulsion?

A

organising cell structures by repulsion at close range

32
Q

What is an example of contact repulsion in humans?

A

Vili: being eroded by the tip and replaced at base by cells being displaced from crypt. Stem cells in the crypt express EphB and flanking cells express ephrinB, as stem cells proliferate they are forced upwards to avoid contact with flanking cells due to repulsive signalling between EphrinB and EphB.

33
Q

What is autocrine signalling?

A

Being able to signal yourself, ie produce signal and have the receptor for it

Cells To Organisms (8 decks)

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