Asymmetry Flashcards
In addition to giving rise to motor neurons, the pMNs of the neural tube also give rise to (2)
Oligodendrocytes and astrocytes
When is the earliest form of asymmetry established
Upon fertilization: sperm enters one side of the cell
Why are tunicates a worthwhile model organism to study?
They are chordates! Have a notochord and then lose it later in development
What is macho-1?
It is a transcription factor which is localized to the vegetal pole of an embryo and macho-1 positive cells are fated to become muscle
In an 8-cell embryo where normally only cell B4.1 expresses macho-1, what happens when the other cells undergo a macho-1 gain of function mutation?
All the cells develop muscle tissue
In an 8-cell embryo where normally only cell B4.1 expresses macho-1, what happens when you perform a loss-of-function experiment using macho-1 antisense knockdown?
All muscle tissue is lost
In an 8-cell embryo where normally only cell B4.1 expresses macho-1, loss and gain of function experiments determined that macho-1 is (1) and (2) for development of muscle tissue
Sufficient and necessary
Cell polarity is important for establishing (2)
- body axes
- tissue regionalization and subdivision
The first cell cleavage in C. elegans is…
Asymmetric
What mechanism is thought to mediate the first asymmetric cell division in C. elegans
Entry of the sperm into one side of the egg
When the sperm enters the posterior side of the egg, what does it “inject” into the egg?
Centrioles: start producing asters (cytoskeletal elements)
What is the name of the membrane marker which marks the sperm entry side of a fertilized egg?
Par2
Par-2 localization establishes the future (anterior/posterior) end of an embryo
Posterior
Define a p-granule
They are perinuclear (surround the nucleus) RNA molecules which are specific to C. elegans, but some other organisms have them
What is the role of p-granules?
Ribonucleoprotein complex (used for translation) which are necessary for specification of germ cells
What is a key role of PAR proteins such as Par2?
Aid in the cellular localization of p-granules around the nucleus
Segregation of p-granules in C. elegans embryo is always mediated by this molecule
Par-2
Describe cell division mapping in C. elegans, how does this contribute to its utility as a model organism?
Every cell division has been mapped which makes it a good model to study because we know so much about it
Describe the localization of p-granule cells as C. elegans grows and divides
P-granules always get segregated into a smaller and smaller cell because only the cells of the germ line will have these granules
At the 1-cell stage, asymmetric distribution of (1) cytoplasmic factors is one mechanism underlying cell fate determination
Intracellular
How might cell division influence asymmetry?
Asymmetric divisions have the ability to redistribute a given factor, this might be enough to trigger different cell fate of the two daughter cells - different “dosage” of intracellular components
What are the 3 key types of sense organs located superficially on the d. melanogaster body
External sense organs, Johnston’s organ, Chordotonal organs
Where is Johnston’s organ located?
Within the 2nd lobe of the antennae
What is the role of Johnston’s organ? What sensory modalities does it detect?
They sense deflection of the 3rd antennal lobe - this allows the fly to distinguish between gravitational, acoustic, and mechanical stimuli
