Block 3 - Final Review (Zaidi & Theisen) Flashcards
What is derived from the ectoderm?
nervous system and epidermis
What is derived from the endoderm?
gut, lungs, and liver
What is derived from the mesoderm?
muscles and connective tissue
What is gastrulation?
Transformation of a hollow sphere of cells in to a gut.
What is meant by cells have “memory”?
Cells retain record of signals their ancestors received during embryonic development.
True or False:
Homologous proteins are not functionally interchangeable.
False - homologous proteins ARE functionally interchangeable.
Genes expressed by cells depend on what?
Environment, both present and past.
What is gene duplication?
Higher organisms have several homologs of the same gene.
What are the two classes of proteins that are most important for development?
(1) Cell adhesion and cell signaling proteins.
(2) Gene regulatory proteins.
Where are the instructions for producing a multicellular animal contained in the genome?
non-coding regulatory DNA associated with each gene
DNA contains regulatory elements that serve as binding sites for gene regulatory proteins
What role does regulatory DNA play in development?
Defines the sequential program for development.
Which portion of DNA defines the sequential program for development?
Regulatory DNA
What role does non-coding regulatory DNA associated with each gene play in development?
Contains instructions for producing a multicellular animal - where gene regulatory proteins bind.
What sequences in DNA make one organism different from another and provides uniqueness?
non-coding sequences
True or False:
Coding sequences in DNA are similar in most organisms, but non-coding sequences make one organism different from another and provide uniqueness.
True
True or False:
Cells make developmental decisions long before they show any outward signs of differentiation.
True
What are “determined” cells?
Cells that are fated to develop into a specialized cell type despite changes in environment.
What are “completely undetermined” cells?
Cells that can change rapidly due to alterations in environment.
What are “committed” cells?
Cells that have some attributes of a particular cell type but can change with environment.
Cells that are fated to develop into a specialized cell type despite changes in the environment are called?
determined
Cells that can change rapidly due to alterations in the environment are called?
completely undetermined
Cells that have some attributes of a particular cell type but can change with the environment are called?
committed
A change in what would allow cells that are born the same (symmetric division) to become different?
change in environment after birth (different molecules induced)
How do cells created from asymmetric division become different?
significant sets of molecules are distributed unequally between daughter cells
What are the most important environmental cues during cellular development?
signals from neighboring cells
induction of a different developmental program in select cells in a homogeneous group leading to altered character = inductive signaling
What is inductive signaling?
Induction of a different developmental program in select cells in a homogeneous group leading to altered character.
What are the two types of signals in inductive signaling?
- short range: cell-cell contacts
- long range: substances that can diffuse through the extracellular medium (morphogens)
What does positive feedback provide cells with?
memory
What is a morphogen?
A long range inductive signal that IMPOSES A PATTERN on a field of cells.
exerts graded effects by forming gradients of different concentrations
each concentration can direct the target cells into a different developmental pathway
In which two was are gradients formed by morphogens?
(1) localized production of an INDUCER that diffuses away from its source
(2) localized production of an INHIBITOR that diffuses away from its source and block the action of a uniformly distributed inducer
Which ligand family binds to receptor tyrosine kinases (RTKs)?
- EGF
- FGF (branchless)
- Ephrins
Which ligand family binds to TGFbeta superfamily receptors?
- TGFbeta
- BMP
- Nodal
What ligand binds to Wnt signaling pathway receptors?
Wnt
What ligand binds to Hedgehog signaling pathway receptors?
Hedgehog
What ligand binds to Notch signaling pathway receptors?
Delta
What do morphogens need?
“on” and “off” switch
How many phases are there in neural development?
3 phases
What happens during phase 1 of neural development?
Different cell types (neurons, glia, muscles cells) develop independently at different locations in embryo according to local program and are unconnected.
What happens during phase 2 of neural development?
Axons and dendrites grow out along specific routes setting up a provisional but orderly network of connections between various parts of the system.
What happens during phase 3 of neural development?
Continues into adult life, connections are adjusted and refined through interactions with distant regions via electric signals.
What phase of neural development do different cell types (neurons, glia, muscle cells) develop independently at different locations in embryo according to local program and are unconnected?
Phase 1
What phase of neural development do axons and dendrites grow out along specific routes setting up a provisional but orderly network of connections between various parts of the system?
Phase 2
What phase of neural development continues into adult life, connections are adjusted and refined through interactions with distant regions via electric signals?
Phase 3
Which phase of neural development does genesis of neurons occur?
Phase 1
Which phase of neural development does an outgrowth of axons and dendrites occur?
Phase 2
Which phase of neural development does the refinement of synaptic connections occur?
Phase 3
What is a growth cone?
An irregular, spiky enlargement on the tip of an axon/dendrites.
What is the irregular, spiky enlargement found on the tip of a migrating axon/dendrite?
Growth Cone
What does the growth cone found on the tip of axon/dendrites during neuron migration?
Crawls through surrounding tissue, trailing the axon or dendrite behind.
True or False:
One of the growth cones starts migrating fast and develops axon-specific proteins, which eventually form an axon.
True
During the migration of neurons during development, what dictates growth cone behavior?
cytoskeletal machinery
What do growth cones throw out that assist them in their migration?
- filopodia
- lamelopodia
What proteins control the assembly/disassembly of actin filaments, which control movement of growth cones?
monomeric GTPases Rho and Rac
What controls the movement of growth cones?
monomeric GTPases Rho and Rac - which control the assembly/disassembly of actin filaments
What are the two major cues that growth cones use to find their way?
(1) Extracellular matrix environment sensed by receptors present on membrane.
(2) Chemotactic factors released by neighboring cells.
What role does chemotactic factors play in growth cone migration?
Secreted by neighboring cells and act as guidance factors at strategic points along path.
May be attractive or repulsive.
Examples:
- Netrin (attractant)
- Slit (repulsive)
- Semaphorin (repulsive)
What are the name of the signals from target tissues that regulate which growth cones synapse and where?
neurotrophic factors
The target cell produces a limited amount of specific neurotrophic factors that are needed for survival. What happens to those axons that do not get enough neurotrophic factors?
Die by programmed cell die.
What are the 2 rules that synaptic remodeling is dependent upon to create spatial order?
(1) Axons from cells in different regions of retina (which are excited at different times) compete for tectal neurons.
(2) Axons from neighboring sites which are excited at same time cooperate/collaborate to retain and strengthen synapses with tectal neurons.
What does activity-dependent synaptic modeling depend on?
Depends on electrical activity and synaptic signaling.
In neuronal development, what depends on electrical activity and synaptic signaling?
activity-dependent synaptic remodeling
What are the characteristics of the epidermis?
- made of epithelial cells
- forms the outer covering of skin
- creates a water barrier
- continuously repaired and renewed
What are the characteristics of the dermis?
- second layer
- rich in collagen
- provides toughness
- loose connective tissue
- dense connective tissue
What are the characteristics of the hypodermis?
fatty subcutaneous layer
What are the multilayered structures of the epidermis, starting at the basal lamina and going superficially?
- basal lamina
- basal cell layer
- prickle cell layers
- granular cell layer
- keratinized squames
- squame
Which cell layer of the epidermis is attached to the basal lamina?
basal cell layer
In what layer of the epidermis are dividing cells found?
basal cell layer
What is unique about the strata made of several layers of prickle cells?
Has numerous desmosomes that attach tufts of keratin filaments.
Which cell layer of the epidermis has cells that are sealed together to form a waterproof barrier?
granular cells in the granular cell layer
Which cell layer of the epidermis forms a boundary between inner metabolically active strata and outer dead epidermis cells?
granule cell layer
What is the outermost layer of the epidermis?
Squame - flattened dead cells densely packed with keratin but with no organelles.
In the differentiation of epidermal cells, some basal cells divide and others move to the layers above it. What changes as cells move through the different layers?
Change in gene expression at each step of differentiation.
Cells start undergoing partial degradation.
Dependent on partial activation of the apoptotic machinery.
Cells lose their nucleus and other organelles.
Time from birth of cell in basal layer to shedding from surface is 1 month.
Why is it important that there are a mixture of cells in the epidermis?
Those that can differentiate and renew worn out cells and those that can remain undifferentiated.
Replace and renew old cells.
Basal layer has dividing cells that differentiate and move to other layers.
What do stem cells provide in the renewal of the epidermis?
Stem cells provide an indefinite supply of fresh differentiated cells.
What are the characteristics of stem cells?
- not terminally differentiated
- can divide without limit
- undergo slow division
- when divide gives rise to 1 cell with stem cell characteristics and the other with the ability to be differentiated
True or False:
Stem cells are tissue specific (e.g., epidermal stem cells, intestinal stem cells, etc…).
True
What are the two theories in the maintenance of stem cells?
- Asymmetric Division –> creates 2 cells, one with stem cell characteristics and another with the ability to differentiate.
- Independent Choice –> division makes 2 identical cells but the outcome is stochastic and/or influenced by environment.
What is the drawback of the asymmetric division theory?
Cannot explain how existing stem cells increase their numbers.
Why is the independent choice theory more supported?
Is more flexible.
Explains the sharp increase in stem cell numbers when needed for repair.
Environment may influence batches of cells and does not have to be 50:50 for every division.
In the regulation of epidermal stem cells, what does contact with the basal lamina control?
Numbers of stem cells.
Maintenance of contact preserves stem cell potential.
Loss of contact triggers terminal differentiation.
What does the loss of contact with the basal lamina of basal cells trigger?
Terminal Differentiation
True or False:
Proliferative potential directly correlates with expression of beta1 subunit of integrin (helps mediate adhesion to the basal lamina).
True
What does the proliferative potential in the regulation of epidermal stem cells directly correlate with?
Expression of beta1 subunit of integrin.
In the basal cell layer of the epidermis, what are the other cells called that are mixed with stem cells that also divide frequently?
Transit Amplifying Cells
leave the basal layer and are incorporated into the layers above
True or False:
Transit amplifying cells are programmed to divide for an endless number of times.
False - programmed to divide for a limited number of times.
transit amplifying cells leave the basal layer and are incorporated into the layers above and are programmed to divide for a limited number of times
What type of receptor are olfactory receptors?
G protein coupled receptor
True or False:
Each neuron expresses only one of these genes enabling the cell to respond to only one class of odorant (organic small molecules).
True
Where are olfactory receptors found?
The free surface of cilia have odorant receptor proteins (olfactory receptors).
Once an olfactory receptor generates an action potential,where is the action potential relayed to in the brain via an axon?
Relay stations in brain called GLOMERULI.
Where are glomeruli located in the brain?
Located in olfactory bulbs - one on each side of the brain.
True or False:
Although olfactory neurons expressing the same odorant receptor are located in different places on the olfactory epithelium there axons converge on the same glomerulus.
True
How long do individual olfactory neurons survive?
only 1 month
What replaces lost olfactory neurons?
Neural stem cells residing in the olfactory epithelium generate replacements for the lost neurons.
Basal stem cells in contact with basal lamina divide and differentiate into olfactory neurons.
In the regeneration of olfactory neurons, what do odorant receptor proteins help in?
Axonal guidance and allow the growth cone to migrate to and establish connection with the correct glomerulus in the olfactory bulb.
True or False:
Regeneration of olfactory receptor cells is one of the only few instances of adult neurogenesis in the CNS.
True
has raised considerable interest in dissecting the pathways for neural development and differentiation in adult organisms
What is a stem cell?
A primitive cell that can either self-renew (reproduce itself) or give rise to more specialized cell types.
Single stem cells differentiate into multiple, functional cell types.
Stem cells functionally reconstitute a given tissue in vivo.
In erythroid differentiation, at what cell type is DNA lost?
reticulocyte
Which type of stem cell can be used to regenerate neuronal cells in the brain?
adult stem cells (bone marrow)
Adipose derived mesenchymal stem cells (AMSCs)
Mesoderm
- cardiac cells
- hematopoietic
- mesenchymal
- smooth muscle
Endoderm
- lung
- thyroid
- pancreas
- gut
- liver
- lungs
Ectoderm
- skin
- neural system
Are founder stem cells pleuripotent, multipotent, or totipotent?
multipotent
maintained in a very small amount in our body
Are founder stem cells embryonic stem cells?
No - multipotent stems cells that are like adult stem cells.
True or False:
Each organ/tissue has a fixed number of founder cell populations programmed to have a fixed number of divisions.
True
What are founder stem cells controlled by?
Short range signals that operate for a few hundred cell diameters.
Define the size of large final structures.
If the adult organ needs to be renewed, founder stem cells can divide as stem cells giving rise to one daughter cell that remains a stem cell and a set of cells that have a set number of transit amplifying divisions.
Can you “trick” transit amplifying cells to keep dividing?
No - they divide a finite number of times and are already determined in what they are going to differentiate into.
True or False:
After division, one of the daughter cells gets all the original DNA strands from all the chromosomes.
True
- *this daughter cell will retain stem cell characteristics**
- *original strand of DNA preserved in stem cells from generation to generation**
- *second cell gets the newly synthesized strand**
- *this is a way to prevent genetic errors in stem cells.**
What are the different types of stem cells?
- embryonic stem cells
- adult stem cells or tissue-specific stem cells
- fetal stem cells
- induced pluripotent stem cells (iPS cells)
What are embryonic stem cells derived from?
Blastocyst stage of embryo.
capable of proliferating indefinitely in culture with unrestricted developmental potential
What can embryonic stem cells develop into?
Different cell types with characteristics appropriate for that site (even germ cells).
if injected into an embryo at a later stage or into an adult they fail to receive appropriate sequence of cues for proper differentiation - often become a tumor
What happens if an embryonic stem cell is injected into a later stage embryo or into an adult?
They fail to receive appropriate sequence of cues for proper differentiation.
Often become a tumor!
The defining feature of an ES cell is its ability to differentiate into a wide range of tissues. Teratomas do not display axis formation or segmentation. Unlike embryos, ES cells on their own are incapable of generating the body plan. This lack of organisation is also seen when ES cells differentiate in vitro.
What cell types can be generated if an embryonic stem cell is given retinoic acid?
- neurons
- smooth muscle cells
Are embryonic stem cells pluripotent or totipotent?
pluripotent
Is the zygote pluripotent or totipotent?
Totipotent
What are the advantages of mature stem cells?
- Immune response is unlikely because patients are using their own cells.
- Some availability (e.g., blood stem cells)
- Partly specialized; require less coaxing to create specialized cells.
What are the disadvantages of mature stem cells?
- Limited longevity; difficult to maintain in cell culture for long periods.
- Difficult to find and extract from mature tissues.
- Many unknowns; not all mature stem cell types have been identified yet.
- Multipotent; limited flexibility; cannot become any cell type to date.
- Uncommon and growing more scarce with age.
- Questionable quality due to genetic defects; targeted disease may still be present in stem cell genes.
What are the advantages of early stem cells?
- Immortal - cell lines remain intact for long periods of time and produce endless numbers of cells.
- Easy to extract in a laboratory.
- Pluripotent - very flexible; can make any body cell.
- Readily available; many blastocysts created by in vitro fertilization are available for research purposes; new methods like SCNT are opening up new potential sources.
- With somatic cell nuclear transfer (SCNT), immune rejection is not an issue because the patients are using their own cells.
What are the disadvantages of early stem cells?
- Immune rejection is possible if stem cells are derived from an blastocyst created through in vitro fertilization (IVF).
What is the best way to generate embryonic stem cells?
Somatic Cell Nuclear Transfer
combines cloning methods with embryonic stem cell technology to produce cells which are custom made for patient
What is one of the large benefits of studying stem cells?
drug discovery
