Describe and/or draw blastula stage of development in a sea urchin. Its morphology (shape and arrangement of cells) resembles that of what genus of alga?
These algae are closely related to what genus of one-celled algae?
How do they swim? (both the algae and the sea urchin blastulae).
*How is this method of swimming related to the usefulness of this genus of single celled algae as a genetic model organism?
Why are sea urchins used for so much research? Are sea urchins one of the genetic model organisms? Why or why not?
What two important kinds of cellular rearrangement occur at the vegetal pole of sea urchin embryos soon after the blastula stage of development?
Does anything like one of these rearrangements occur in the normal development of Volvox?
What is the defining property of the vegetal pole of an embryo?
What could you reasonably hope to learn about the proteins needed for gastrulation by finding mutations in frogs which cause gastrulation to fail in embryos that are homozygous for this mutation?
Trying to isolate as many as possible different mutant lines that are defective in some particular property is called a ....... ......?
Gastrulation is a process in which what moves where, and the cells of an animal embryo are subdivided into the 3 what? Name these 3?
What are some organs that develop from each of the 3?
What is neurulation?
Where does gastrulation begin in frog embryos as compared with sea urchin embryos?
What is the stomodeum?
Where is it located relative to the blastopore?
How is the archenteron related to the blastopore and to the stomodeum?
Teeth develop from which two parts of vertebrate embryos?
What kind of stimulation occurs when these two kinds of embryonic cells come into contact?
Compare gastrulation in human embryos versus bird embryos; what about as compared with gastrulation in frog embryos, and in sea urchin embryos?
What is the genetic evidence that multicellularity must have evolved separately many times?
Describe the process by which Dictyostelium becomes multicellular.
In terms of cell movements, contrast gastrulation in animal embryos with "fruiting" in Dictyostelium slugs.
If you separate the first two cells, or even the first 4 cells, of a sea urchin embryo, each can form a whole, normally-proportioned pluteus: what equivalent experiment can you do with Dictyostelium slugs?
What is the evidence that Dictyostelium amoebae use chemotaxis?
If you had several chemicals that you suspected of being chemotactic attractants for cells of a given species, how would you test them?
Imagine that cells of the archenteron of a frog embryo became chemotactically attracted to cells of the stomodeum, what should happen?
*Suggest experiments that could disprove such chemotaxis as a guiding mechanism of gastrulation.
If such chemotaxis did occur, then genetic mutations in genes for what sorts of proteins would result in abnormal gastrulation?
**Conversely, suppose that some new genes are discovered in frogs and named the "no-mouth" gene or the "two-mouth" gene, or a "cyclops" gene, then how might these be related either to gastrulation or to stomodeum formation?
Contrast chemotaxis to what is meant by embryonic induction?
The lens of the eye needs to develop from the part of the somatic ectoderm directly above the eye cup (a part of the brain); this alignment is produced by induction;
* But suggest how chemotaxis might also or instead contribute to such proper positioning of anatomical structures.
Compare and contrast a mammal egg cell with that of a frog, a bird, and a sea urchin. Compare cleavage in each of these kinds of animals.
What is a micromere?
What and where is the blastocoel?
*Compare the formation of the skeleton in sea urchin embryos as compared with skeleton formation in vertebrate embryos.
What are somites? The cells of somites subsequently rearrange into what 4 subdivisions?
What is paraxial mesoderm? What is lateral plate mesoderm? What is intermediate mesoderm?
From what part of mammal embryos does the heart develop? What do kidneys develop from?
What and where is the notochord?
In terms of their embryological development, how are the lungs similar to the liver?
What are five specific examples of differentiated cell types in humans?
From which of the primary germ layers does each of these cell types differentiate?
In molecular terms (DNA, and all that), what does differentiation result from?
In principle, what change in what DNA sequence ought to be able to cause the hemoglobin protein to be synthesized in nerve cells?
About how many differentiated cell types are there in the human body? About how many different genes do we have?
*Suggest a likely relationship between embryonic induction and promoter regions of genes.
What is the evidence that all the cells of the body (except for certain special ones) have all the same genes as all the others?
Prevention of embryonic induction could, in principle, result from mutation in genes of any of the following kinds..?
For example, the genetic reason that birds lack teeth could be because of mutations in genes for what? or what else? (as many different sorts as you can think of)
By what experiments (involving grafting of tissues, or tissue culture, or something like that) could you distinguish between these various possible genetic explanations for lack of teeth, in a given kind of animal?
What are 5 or 10 specific examples of genetic model organisms? What are 4 or 5 criteria by which species are selected to be model organisms?
In Chlamydomonas, what process is analogous to the fertilization of egg cells by sperm in multicellular animals?
Are the resulting cells diploid or haploid? Explain?
For the purpose of genetic studies of photosynthesis and of the active bending of flagella, what advantages does Chlamydomonas have relative to (say) corn or Paramecia?
Based on your knowledge of the Dictyostelium life cycle, this organism would be especially good for studying the genetic and molecular mechanisms of what different general biological phenomena (which also occur in humans)? (at least 3 or 4 such phenomena).
What is the name of the scientist who discovered Dictyostelium discoideum, and where did he get his undergraduate degree (hint: not Duke).
What do embryologists mean by "regulation", in relation to the formation of bodies?
Compare the mechanical structure of the notochord with that of the Dictyostelium stalk. What are 2 similarities and at least one difference?
What molecular evidence proves that multicellularity must have evolved separately several times in Volvox?
About how many different species are there in the genus Chlamydomonas?
*From what lower group of plants did higher plants evolve?
What are the dermatome, myotome and sclerotome?
What is paraxial mesoderm?
What are the names of four important kinds of transcription factors? What class of molecules are transcription factors?
What is the function of transcription factors? What do they bind to? Producing what effect?
What phenotypic effects could be produced by mutations in the genes that code for transcription factors?
What about mutations in the genes for the binding sites of transcription factors?
What is the distinction between (and the relation between) promoter regions and enhancers?
If ten different genes had the same or nearly the same base sequences in their promoter regions, then would you expect these genes to be expressed in the same or different differentiated cell types?
Do the genes for transcription factors have their own promoters?
*Suppose that a given transcription factor were to bind specifically to the promoter for its own gene!? (i.e. the promoter region for the gene that codes for that same transcription factor!) Is that possible?
How could it be related to whether the differentiated state is permanent, or self-perpetuating, even if reversible?
In what way was the birth of Dolly the sheep evidence that differentiation can be reversible?
What do embryologists mean by "genetic equivalence"?
What is "nuclear transplantation"? About what year was this method first successfully accomplished?
** Is it the same or different that "cloning"?
Are there any exceptions to the rule that all the cells of the body have all the same genes as other cells?
How does the immune system (vaccination, and all that) depend on certain differentiated cell types NOT having quite all the same genes?
Hint: Do all differentiated cells of these types have the same DNA sequences as each other? Or some sequences different from other cells of that same cell type?
*If Dolly the sheep has been produced using a nucleus from a B-lymphocyte, then why would she have only been able to make antibodies against one single antigen?
What are four different levels at which gene expression can be controlled?
What is meant by transcriptional control?
Is it sometimes possible for genes to be transcribed in many cells, but only some of these cells to make mRNA out of the transcripts.
How is it possible for many embryos to begin protein synthesis at a high rate right after fertilization (and to do so even in the presence of poisons that selectively block RNA synthesis)?
Synthesis of milk protein is stimulated by certain hormones by what means other than stimulating synthesis of more messenger RNA for this protein?
What is Hensen's node? At what stage of development, and in which kinds of animals, does Hensen's node form?
How is it related to the primitive streak? How is it related to the notochord?
*In the conjoined twins from Iran who were joined at the head, and who recently died in a surgical attempt to separate them, can you figure out approximately what must have gone wrong during their original embryonic development?
How many trophoblasts must there have been? How many inner cell masses did they develop from? How many primitive streaks?
Could there have been two Hensen's nodes regressing away from each other, in opposite directions along the same primitive streak, in the same inner cell mass, inside the same trophoblast, descended from one original fertilized egg?
Can you figure out what their embryo must have looked like at the stage of neurulation?
What do embryologists mean by "invagination", "cavitation", "epiboly"?
*Is it surprising that the neural tube develops by cavitation in teleost fish, but by epithelial folding in almost all other vertebrates?
Contrast the pattern of cell movements in gastrulation of birds and mammals, as compared with gastrulation of amphibians.
*In the evolutionary intermediates between amphibians and reptiles, by what paths or mechanisms do you suppose the future mesoderm cells moved into the interior?
What are meant by epiblast, hypoblast and mesoblast?
What are the differences between epithelial cells and mesenchymal cells?
Are there any embryonic phenomena in which epithelial cells become mesenchymal?
**If mesenchymal cells become epithelial again, is that cavitation?
What is the purpose of making "northerns"?
What is the function of electrophoresis?
Does it separate molecules according to size? **Or according to charge?
*What does "blotting" accomplish, in comparison with electrophoresis?
What is meant by the polymerase chain reaction (=PCR)? How is heat involved?
Would it be possible without the heat-resistant DNA polymerase from the organism from the hot springs in Yellowstone National Park?
Why do these polymerases make PCR a lot less work and cheaper?
What function is served by the "primer" DNA sequences in PCR?
What is meant by "in situ hybridization"?
What function does this method serve in embryological research?
* Might it be used to study a case of embryonic induction?
What are "microarrays"? How can they be used to find out which genes are being transcribed in a given tissue or stage of embryonic development, and which are not being transcribed?
* More specifically, how could you compare which base sequences are found in transcripts from one differentiated cell type as compared with another cell type?
What is meant by transgenic organisms? (*Or do you prefer the term "Genetically Modified"? Is mutation genetic modification?)
*Is there any particular difficulty in introducing genes from one species into the DNA of another species?
*What about putting plant genes into animal chromosomes, or the reverse?
Are chimeric animals the same as hybrids? (Hint: no!) What is the distinction?
**Can you figure out why the immune system doesn't attack tissues in chimeras? (Nor in hybrids, either).
**Suppose that DNA coding for the antibody protein were used as a transgene to make transgenic mice: how could affect the immune system of the transgenic mice?
What are the similarities and the differences between RNA-i (=RNA interference) in comparison with "antisense RNA"?
*Can you invent some hypothetical experiments to find out whether antisense RNA in a given case was really having its effect by the same mechanism as RNA-i?