BZ311 Final Exam Study Guide Unit 3
Name the three basic elements of the limb in order from distal to proximal.
1) Autopod 2) Zeugopod 3) Stylopod
The pax6 gene contains two highly conserved sequence regions, termed the _______________ and the ______________.
1) Paired box 2) Homeobox
Which two morphogentic paradigms are highly applicable to skin formation in humans?
1) Replenishment by stem cells that continuously divide 2) Autocrine signaling
Predict what other phenotypes a dalmation is most likely to have.
A defect in some of their sensory neurons or glia, or defects in intra-membranous bone formation.
A mouse mutant was found that overproduced pheomelanin and underproduced eumelanin. What color do you predict the mouse will be?
A mouse with reddish hair
FGFR's are critical for bone development. Mutations in the FGFR3 gene cause what human condition?
Achondroplasia (Dwarfism)
In a neurula, the ectoderm covering the neural tube was removed and a chunk of the notochord from a donor embryo was added above the notochord. What will develop?
An extra floor plate.
What adhesion protein do neuroblasts make that allows them to adhere tightly to the guidance cells?
Astrotactin
Where is the ZPA located in the limb bud?
At the posterior of the limb bud
A new species of fish was found having very small widely spaced eyes. Investigators looked at the expression of Shh and Pax6, based on the phenotype what will the Pax6 expression look like?
Barely detectable or absent in the head
KFG is an autocrine growth factor made in basal keratinocytes. It stimulates high rates of cell division in what type of cells?
Basal Keratinocytes
Myostatin in a paracrine factor that regulates MyoD. MyoD is necessary for muscle development. Cows that had a loss of function mutation in myostatin. What do you predict the phenotype will be?
Beefy cows with extra muscle
Predict what phenotype will happen if we make a transgenic cow that overexpressed FGFs in the developing muscle cell progenitors
Beefy cows with extra muscle
Transplant experiments showed Hox gene patterning occurs in the mesoderm ___________ the formation of somites.
Before
Based on quail-to-chick transplants when do the Hox genes exert their effects on anterior/posterior patterning of the midline?
Before the somites form in the paraxial mesoderm
After a period of growth the hair follicle goes into a state of controlled regression called what?
Catagen
Name the committed mesenchymal cells that will first proliferate and then become hypertrophic in bone development
Chondrocytes
What is the origin of the lens placode?
Derived from a region of the ectoderm that covers the outside of the neurula state animal.
A type of bone formation that involves the formation of a cartilage intermediate is known as what?
Endochondral ossification
When first forming close to the neural tube neural crest cells change their arrangement in the tissue they will under go a ____________ to ____________ transition.
Epithelial to mesenchymal
When first forming, close to the neural tube, neural crest cells change their arrangement in the tissues and undergo a _____________ to ___________ transition.
Epithelial to mesenchymal
Cells in a __________________ all share the same developmental potential. Meaning ANY cell initially has the potential to become a hypoblast or neuron.
Equivalence group
If a cell continues to express high amount of delta it will also do what?
Express high levels of proneural genes and acquire neuronal cell fates.
What phenotype occurred when Pax6 was homozygous mutant (-/-) in Drosophila?
Eyeless, no eye development.
The bat wing has a very large autopod and reduced stylopod and zuegopod. Predict a gene that could be overexpressed to increase autopod size.
FGF or WNT
Name the paracrine factor gene that is one of the earliest genes to be expressed in regions where limb buds form, and is responsible for the outgrowth of limb buds.
FGF-10
The following proteins are important in limb development. TBX4, TBX5, Shh, Wnt17, FGF10, RA, and FGF8. Which protein is critical for the initiation of lib buds in the flank?
FGF10
True/False: The notochord becomes the adult spinal chord.
False
True/False: The proneural genes encode transmembrane proteins
False
True/False: Shh acts as a morphogen. It is released from the ZPA and diffuses across the entire limb bud, setting up a morphogen gradient, directly patterning tissues according to its concentration.
False, it sets up a gradient of BMPs because Shh cannot penetrate cells very deeply.
True/False: Ectopic expression of Pax6 in a frog resulted in a fundamentally different phenotype than ectopic expression of Pax6 in the fly.
False, they are fuctionally homologous.
True/False: Humans that are heterozygous for Pax6 mutations have no obvious phenotype in the eye
False, they have aniridia.
True/False: Hox genes are important to specify somite identity, but they only begin to operate once a somite has finished "pinching off" from the mesoderm.
False, they operate in unsegmented paraxial mesoderm.
What does a homozygous mutant (-/-) in SHH result in?
Fewer digits
What set of cells later provides an additional, second source of Shh?
Floor plate cells
As brain development proceeds, newborn neuroblasts are guided to their destination by crawling along _________ until they reach the correct layer.
Glia
FGF5 regulates the progression from anagen to catagen. If a mouse produced too much FGF5 how do you predict hair growth is affected?
Hair length will be shorted than the wildtype
Name the two highly conserved regions of the Pax6 gene.
Homeobox and paired box
In a HoxA11 homozygous mutant, the ulna and radius (in the forming arm) were completely normal. What is the best hypothesis for this result?
HoxA11 is genetically redundant with another paralog, like HoxD11.
Floor plate cells are found where?
In the neural tube
In the germinal neuroepithelium after a cell completes mitosis one daughter cell will migrate outward and take up residence in the peripheral layer. What happens to the second daughter cell?
It does not migrate, but remains behind and eventually divides again.
In a drosophila embryo, a mutant was discovered in which ALL cells of the nueroectoderm equivelance group continuously expressed Delta, in contrast to 3/4ths of these shutting down. What will the embryo make less of?
It will make far less neurons than normal.
Cell engaged in lateral inhibition are using what kind of cell signaling to sort out cell fates?
Juxtacrine signaling
What protein in hair is extremely abundant and forms rope-like coils of amino acid chains?
Keratin
What type of hair is found on the human fetus?
Lanugo hair
Based on an excess amount of delta expresssion what morphogenetic paradigms have failed?
Lateral inhibition and Juxtacrine signaling
The optic cup and the _______________ interact by reciprocal induction to create the lens vesicle.
Lens placode
In a young chick, unsegmented paraxial mesoderm was cut from the area that would normally give rise to lumbar vertebrae. It was transplanted to a host embryo in a region that gives rise to thoracic vertebrae. The transplanted tissue should give rise to what?
Lumbar vertebrae, because it is already differentiated.
Predict what differentiated cell type normally found in the epidermis of adults, is missing from areas of the coat with white coloring.
Melanocytes
A new somite is "pinching off" into a discrete, physically separated ball of cells, when these cells change their arrangement in the tissue they undergo a ___________ to ___________ transition.
Mesenchymal to Epithelial
When neural crest cells encounter cells expressing ephrin, they will do what?
Migrate away from these cells
What does a double homozygous mutant (-/-) for Shh and Gli3 result in?
More digits
What does a homozygous mutant (-/-) in Gli3 result in?
More digits
Name one gene that if overexpressed in a fibroblast cell, could convert that cell into the muscle cell fate.
MyoD or Myf5
MyoD and Myf5 are MRFs. What does MRF stand for?
Myogenic Regulatory Factor
What subdivided portion of the somite will give rise to msucle?
Myotome
What are the progenitor cells for muscle development?
Myotomes
What is it called when myotome cells align into rows and fuse into multinucleated muscle cells?
Myotubes
A dalmation dog has a black and white spotted coat and is also deaf. Predict what migratory cell type could cause both phenotypes if fewer of these cells were formed or didnt migrate consistently.
Neural Crest Cells
Implantation of a noggin bead between presumptive digits 2 and 3 results in what?
No change in digit number, but at should result in a change in the identity of digit to to look more like digit 3.
What receptor/ligand pair of proteins operates by juxtacrine signaling to initiate a pathway of genes that culminates in a new somite boundary being formed?
Notch/Delta
Floor plate cells initially receive Shh from what cells?
Notochord cells
A myotome cell is different than a myotube because the latter has multiple what?
Nuclei
The somites arise from the _____________ mesoderm in the neurula.
Paraxial
Following neurulation, the somites will arise from what type of mesodermal tissue?
Paraxial Mesoderm
Name the pigment that gives hair a reddish color?
Pheomelanin
What limb axis does the dual gradient model explain?
Proximal/Distal
Name a signaling paradigm used in eye organogenesis that involves multiple rounds of cross-talk between adjacent tissues, in order to establish the fates of cells in different layers.
Reciprocal induction
Neural crest cells Eph receptors: Ephrin, the ligand is expressed on cells of the posterior ____________.
Sclerotome
What do we term the protion of the sub-divided somite that is closet to the notochord?
Sclerotome
The name for the somite when it is newly-forming is what?
Somitomere
The newest barely forming somite is known as what?
Somitomere
In a neurula, the ectoderm covering the neural tube was removed and a chunk of the notochord from a donor embryo was added above the notochord. What paracrine factor will be overproduced?
Sonic Hedgehog (Shh)
The following proteins are important in limb development. TBX4, TBX5, Shh, Wnt17, FGF10, RA, and FGF8. Which protein is critical for the identity of the bud as hindlimb not forelimb?
TBX4
What gene product will be required for a limb bud to establish its identity as the forelimb rather than the hindlimb bud?
TBX5
In a neurula, the ectoderm covering the neural tube was removed and a chunk of the notochord from a donor embryo was added above the notochord. The development of what body organs will be seriously defective?
The Brain, central nervous system, or spinal chord.
Once the neural tube developes 5 vesicles, which vesicle gives rise to the optic cup?
The Diencephalon
What axis of the limb is duplicated if a second ZPA is surgically introduced to the limb bud mirroring the locatinon of the first limb bud?
The anterior posterior axis
What would happen if the limb bud cells at the very tip of the limb bud are surgically removed?
The limb bud ceases to grow into a limb
What term describes a source of neural crest cells prior to neurulation?
The neural folds
In a neurula, the ectoderm covering the neural tube was removed and a chunk of the notochord from a donor embryo was added above the notochord. Not counting the notochord itself, which region of the mesoderm will be most affected by this transplant?
The paraxial mesoderm, because it also relies of Shh signals from the neural tube.
What is the job of chondroclasts in bone development?
They will eat debris left by apoptotic hypertrophic cells
What will eventually happen to chondrocytes
They will undergo apoptosis to make room for osteoblasts
The molecular function of Pax6 is what?
Transcription factor
The T-box genes function as what?
Transcription factors
The molecular function of the Pax6 protein is what?
Transcription factors
True/False: A bat wing, a human arm, and the whale flipper all have the same basic elements to the limb but they are all different in size and proportion.
True
True/False: Data suggests that the colinearity principle applies to the limb as well as the A/P body axis
True
True/False: Delta is an example of a neurogenic gene
True
True/False: Ectopic expresssion of Pax6 in an amphibian resulted in ectopic eye tissue development at several places around the body.
True
True/False: In the reeler mouse mutant, the developing brain contains cells of the correct fates, but its mostly the non-layered arrangement of these cells that is the reason for this phenotype.
True
True/False: Pax6 expression is necessary and sufficient for development of ectopic eyes in drosophila
True
Fine soft hairs found on newborn baby or on the forehead of an adult human are called what?
Vellus Hairs
What type of hair would be found on the human forehead?
Vellus hair
A new species of fish was found having very small widely spaced eyes. Investigators looked at the expression of Shh and Pax6, based on the phenotype what will the Shh expression look like?
Very broad in the midline.
Yes/No: Are newborn neurons ever regenerated in the adult brain?
Yes
In a neurula, the ectoderm covering the neural tube was removed and a chunk of the notochord from a donor embryo was added above the notochord. Will the embryo lack dorsal neural tube fates?
Yes it will
In a drosophila embryo, a mutant was discovered in which ALL cells of the nueroectoderm equivelance group continuously expressed Delta, in contrast to 3/4ths of these shutting down. Will the neuroectoderm cells continue to express proneural genes?
Yes it will, because Delta is still present.
Does mitosis continue to occur in the mature CNS, that is are new neurons born once the CNS is mature?
Yes, new cells can form via mitosis in the CNS once it is mature.
What does ZPA stand for?
Zone of polarizing activity