REVIEW QUESTIONS FOR FIRST EXAM BIOLOGY 104 EMBRYOLOGY SPRING 2005Its 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? What two important kinds of cellular rearrangement occur at the vegetal pole of sea urchin embryos soon after the blastula stage of development? 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? 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? What is the genetic evidence that multicellularity must have evolved separately several different times in Volvox? 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 or prove 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; What and where is the blastocoel? 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? 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? 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 is "nuclear transplantation"? About what year was this method first successfully accomplished? * Is it the same or different than "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 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 "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?
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