What are the essential processes involved in multicellular development?
Cell proliferation, cell specialization, cell interaction, and cell movement
How do cell differentiate?
They all start the same, but they respond to the signals from neighboring cells to know what they will differentiate into which is called (inductive signaling)
T/F Signals have to be come from cells directly in contact
False. It can come from a diffusible molecule, from a long range or in direct contact.
How do morphogens work?
Imagine a line of undifferentiated cells. Morphogens start from the left most cell and diffuse their way down the line to the right. The cells closer to the source will have a higher concentration, while the cells farther away will have a lower concentration. The range of concentrations will determine what the cell will differentiate into.
Does one signal determine the entire fate of all cells?
Nope! Multiple combinations of different signals will determine what the cell will be when it "grows up" haha. It also will remember previous developmental signals/events
What is lateral inhibition?
When the a cell gets excited (signals) the one nearby it is still getting the signal but to a much less extent because the main cell is blocking it (inhibition)
Asymmetry is self-amplifying meaning that it is a ________
Positive feedback loop
What is the difference between symmetric and asymmetric division?
Symmetric division means they divide equally, but due to external signals will differentiate. Asymmetric division means they divide unequally from the start
How does the Notch Pathway work?
For ex: 2 undifferentiated cells in close contact. Each one has a Notch receptor and a Delta ligand in their membrane. Each will compete by trying to inhibit the other cell until it becomes the specialized cell
What happens to Notch after the Pathway is complete?
It is cleaved 3 times. ADAM will cleave the Notch receptor from where it is docked. The remaining of the receptor gets cleaved as well. Then a Gamma-secretase will cleave the tail on the inside off and the tail migrates to the nucleus.
What is Wnt?
It's a series of growth stimulating factors
Why is B-catenin dangerous if not degraded?
It can lead to higher levels of B-catenin and can cause the cell to become carcinogenic because it translocate to the nucleus and transcriptionally activates a group of genes
What happens if the Wnt signaling pathway is stopped?
Cell proliferation and differentiation will decrease dramatically leading to developmental abnormalities and cancer diseases
How doe axin play a role is regulating B-catenin? What will happen if Wnt signaling is connected to the Frizzled receptor
It ubiquinates the B-catenin and makes it degrade. When Wnt binds, it calls the axin over to and leaves B-catenin unattended.
What is a single membrane protrusion on the surface of most vertebrate cells called?
Primary cilium
Describe how the cell is without Hedgehog.
The receptor Patched inhibits Smoothed which allows Gpr161 turn on Gli3 (transcriptional repressor). Birth defects will occur
Describe how the cell is with Hedgehog
Patched is being occupied with the Hedgehog signal. Smoothed removes the 2 proteins (Patched and Gpr161) and Smoothed is left to its own devices on the primary cilium. In moving there, Smoothed leaves Sufu (inhibitor of Gli2) unattended allowing Gli 2 to move into the nucleus and transcribe target genes.
* Inflammatory stress signaling through NFkB
Slide 16
How nuclear receptors function as transcription factors
Slide 17-19
Understand how circadian clocks are negative feedback pathways
The TIM proteins makes you sleepy. In the daytime, sunlight causes degradation of the TIM protein
T/F Multicellularity evolved independently in plants and animals
True! Plants don't have pathways like Hedgehog, Wnt, Notch etc. Humans don't have chloroplasts
Animals use _______ kinases while plants mainly use ______ kinases
Receptor Tyrosine Kinase (RTKs), Serine/ Threonine kinases
How does ethylene work?
Without it binding, the EIN3 will be degraded. (plant won't grow/ develop more). When it binds, EIN3 is left alone to further develop and ripen the plant
How does Auxin hormone work?
Cells in the roots will direct roots to grow downwards by send a bunch of auxin over to the area. Auxin will help activate the growth factor. Without it, the growth factor will degrade
How does Phytochromes and Cryptochromes work?
Phytochromes are activated by red light to phosphorylate themselves to control transcription. Cryptochromes just sense blue light.