Signalling Flashcards
What is long range signalling known as and how does it work?
endocrine signalling
release of hormones into the bloodstream in animals and through the vascular system in plants
Give an example of an endocrine signal in plants and its function.
the TF ‘CO’ accumulates in sunlight
when levels are high it promotes synthesis of FT signal protein which moves through sap from leaf to shoot which promotes flowering
What is a cell that can respond to a certain signal said to be?
competent
What is paracrine signalling?
intermediate range signalling
What is juxtacrine signalling?
contact dependent (cell-cell) signalling
During nerve system development, how do axons find and connect to other nerve cells?
by use of a growth cone at the end of the axon
guided by guidance molecules secreted along its route
grow towards attractive cues and grow away from repulsive cues
What are the basic steps to a nerve signal?
- electrical signal propagates from cell body of ‘presynaptic cell’ along its axon
- the two cells contact each other at the synapse where the axon of one cell touches the cell body of another
- electrical signal propagates along ‘post synaptic cell’
What is the SRY?
Sex determining Region Y chromosome
a TF on the Y chromosome
regulates gene expression leading to testes differentiation
How does the SRY signal promote development of male sex organs?
during development the embryo has both male and female structures
SRY signal causes the gonads to become testes (not ovaries)
allows male structures (Wolffian duct) to persist and the female structure (Mullerin duct) to dissapear
What is meant by the ‘default’ in regards to cell signalling and give and example?
this is what happens unless a signal instructs an alternative fate
eg development of female sex organs, happens unless SRY signal is recieved
Sexual dimorphism in birds is similar to humans in what ways?
have unequally sized sex chromosomes, male (ZZ) and female (ZW)
male and female embryos are initially indifferent
What is the definition of a mosaic?
genetic change in cell lineage derived from a single zygote
what is the definition of a chimera?
fusion of genetically distinct embryos
What is a gynandromorph?
an organism with both male and female features
What is meant by cell autonomous sex determination?
cells have intrinsic sex identity eg in chickens
longe range signalling is not primary component driving sexual dimorphism
What is the sex determination mechanism in alligators?
temperature
known as temperature dependent sex determination (TSD)
What do the different mechanisms of sex determination indicate?
signalling evolved to produce two sexes
two sexes didn’t produce signalling
What is meant by the proximo-distal axis?
proximal ————————————-> distal
close to body distant from body
What is meant by the proximo-distal axis?
along body axis
eg head anterior, feet posterior
eg thumb anterior little finger posterior
What is the AER?
Apical Ectodermal RIdge
found at the tip of growing limb bud
promotes limb growth along proximo-distal axis by way of secreting signal proteins
What is the signalling protein secreted by the AER?
FGF4, belonging to a family of secreted growth factors
FGF4 soaked beads can substitute the AER in limb growth
What is a morphogen?
a substance active in pattern formation whose spatial concentration varies and to which cells respond differently at different concentrations
What model explains development of digits along the anterior-posterior axis?
french flag model
What is the ZPA?
Zone of Polarising Activity, found on the chick limb that produces a morphogen whose concentration along developing limb determines digit formation
What protein is secreted by the ZPA?
sonic hedgehog (Shh)
What is an organiser?
a signalling center that directs the development of the whole embryo or part of the embryo
eg ZPA
How do trichomes ensure even spacing?
release signalling protein triptychon which inhibits neighbouring cells from becoming trichomes
v similar mechanism in drosophila hairs with the Notch signalling pathway, even though no similarity between notch and triptychon sequences
How does juxtacrine signalling aid the formation of crypts in the gut?
EphB+ and EphrinB+ repel each other when in contact
during crypt development EphB+ cells are flanked either side by EphrinB+ cells so to escape have to move downwards thus creating a crypt
What is autocrine signalling?
a cell responding to its own signals
What two types of signalling are used in nerve growth cones.
Paracrine (Slit/Robo and Netrin/DCC)
Juxtacrine (Eph/Ephrin and Semaphorin/Plexin)
Which side if the axis is the ZPA located?
The posterior side
What is the name of the process by which drosophila hairs and plant trichomes are spaced?
Lateral inhibition
