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178 Cards in this Set
- Front
- Back
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What structure in Xenopus sends signals to specify the anterior-posterior axis?
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The organizer
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What is a syncytium?
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In drosophila when the DNA is replicated, but the cytoplasm does not.
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What does Pax-6 regulate in flies, squid, mice and humas?
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eye development
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What induces formation of the eye's lense, and what must be true for this to occur?
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The optic vesicle induces formation of the lense, but the cells must be competent to receive the signal. (Cells in other regions of the body cannot be induced to form lenses even if an optic vesicle is moved to that location)
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What allows the surface ectoderm to respond to the signal from the optic vesicle.
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Pax6
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What do mutations in Pax3 cause phenotypically?
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White patch of hair, different color eyes, deafness
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What is a syndrome?
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A group of linked human malformations that are caused by a common genetic defect.
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What gene mutations cause Piebaldism?
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Kit gene (humans) and white spotting gene (mice)
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Why do White and Steele mutated mice have the same phenotype?
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The two genes function in the same signaling pathway. One gene encodes for the ligand and the other encodes for the ligand's receptor.
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What does Steele encode?
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The ligand (stem cell factor)
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What does White encode?
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The receptor (c-Kit)
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What occurs when a mutant cell does not have a ligand?
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The neighboring cells can make the ligand, rescuing the cell.
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What occurs when a mutant cell does not have a receptor?
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The cannot be rescued by neighbors as there is no way for them to perceive the signal from neighboring cells.
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What is mosaic pleiotropy?
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A gene is independently expressed in several tissues.
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What is relational pleiotropy?
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A gene product is needed by only one particular tissue, but another tissue relies on the first for signaling proper development.
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What leads to Waardenburg Syndrome II?
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Mutations in MITF
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What cells are used to maintain the skin?
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Specialized stem cells.
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Where are cells "born" in the epithelial lining of the gut?
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the bottom of the "crypt"
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Where are cells release in the epithelial lining of the guy?
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The villus
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How long does it take for a cell to move from the bottom of the crypt to the release from the villus?
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3-6 days
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How are muscle stem cells kept from differentiating?
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Growth factors preserve them
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What type of stem cells can create all blood and lymph cells?
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Hematopoietic stem cells
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Where are adult stem cells found?
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nerve cells, blood cells, muscle cells, bone cells, and stem cells.
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What are adult stem cells classified as?
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Multipotent, they can form a number of tissues, but not all
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What other type of cells are considered multipotent?
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Umbilical cord cells.
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How can differentiation of stem cells be controlled?
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Changing culture conditions
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How are stem cells tumorigenic?
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Undifferentiated ES stem cells will form tumors if injected ectopically.
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What are the lineage restrictions that limit clinical use of stem cells?
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hormones, extracellular matrix, and cell contact all control when cells are differentiated and to what level.
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What is the similarity between cancer and stem cells?
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Cancer cells continually divide without differentiating, just as stem cells do.
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What must a cancer cell do to become "invasive", and what are the steps in doing so?
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A cancer cell must cross the basal lamina to become invasive. This is accomplished by laminin receptors in the cells binding to type IV collagen in the basal lamina. Type IV collagenase is release by the cancer cell, digesting the basal lamina.
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Once a cell has become invasive, what must happen for it to metastasize?
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The cells must then invade a capillary where they travel to other parts of the body. Somewhere in the cardiovascular system, they adhere to the capillary wall. Once they escape through the capillary wall, they continue to divide, creating a new tumor.
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How was a normal colon cell form a malignant tumor?
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Initially, a single mutation causes a polyp to form. Eventually, more and more mutations will cause the polyp to grow and eventually become a malignant tumor which can then metastasize to other tissues.
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How can a gain of function mutation create a tumor?
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A gain of function mutation in a proto-oncogene creates an oncogene which allows for excessvie proliferation and survival.
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How does a a loss of function mutation create a tumor?
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A loss of function mutation can inactivate a tumor supressor gene. If this only occurs in one chromosome, there is no effect, but if it occurs in both copies, the tumor suppresor gene is eliminated and cells proliferate.
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What causes a predisposition to colon cancer?
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Familial adenomatous polyposis (FAP)
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What is traditionally true in patients with FAP?
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APC of the Wnt pathway is usually mutated.
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How does a gain of function mutation activate an oncogene?
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The mutation permanently activates a signal transduction pathway so that the pathway is always "on".
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What is the function of retinoblastoma?
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Retinoblastoma prevents cell proliferation.
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What causes retinal tumors?
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Retinoblastoma gene mutates, allowing cell proliferation to continue.
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What is true of th retinoblastoma gene in order for a tumor to form?
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Since there are two copies of the retinoblastoma gene, both must be mutated for the tumor to appear.
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What type of virus can cause cancer and how?
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Vetrovirus takes its RNA and reverses transcription forming DNA which can integrate into the genome of the host. The enzyme that changes the RNA into DNA is called reverse transcriptase. When DNA is inserted near an oncogene, it can be permanently turned on, causing the formation aof a tumor.
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How can viruses effect the retinoblastoma protein?
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The retinoblastoma protein must bind to the cell proliferation factor to prevent cell division. A viral protein can bind to the retinoblastoma protein preventing it from binding to the cell proliferation factor. p53, another protein that stops the proliferation of retinal cells, can also be stopped in this manner. This causes the cells to rapidly proliferate and cause tumors to form.
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What are embryonic stem cells?
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Cells that have been removed from the inner cell mass of an embryo during the blastocyst stage and coaxed into growing in culture.
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How can embryonic stem cells be used to create an organism?
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They can be injected into another embryo in the blastocyst stage. The ES cells are usually taken from a mouse with a different coat color than the donor embryo. This serves as confirmation that the ES cells were taken up as a sucessful transgenic mouse will have multiple coat colors.
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What cells in oogenesis transcribe mRNA?
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Nurse cells
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What is the phenotype of a bicoid mutant larva ?
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It has no head, and two posterior regions
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What does the bicoid gene encode?
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Head structures in drosophila.
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What moves bicoid and nanos to their respective locations?
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Motor proteins
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Where is bicoid located?
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The anterior region.
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Where is nanos located?
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The posterior region.
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What protein does nanos bind with? What part of nanos binds?
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The 3' UTR of Nanos binds to Oskar
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What region of mRNA determines the location of the protein?
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The 3' UTR
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What motor protein does the 3' UTR of oskar bind to and where is it transported to?
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Oskar binds to kinesin and is transported to the posterior region.
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What motor protein does the 3' UTR of bicoid bind to and where is it transported to?
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Bicoid binds to dynein and is moved to the anterior end.
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What are hunchback and caudal?
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Maternally deposited mRNA.
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What effect do bicoid and nanos have on hunchback and caudal?
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Bicoid and nanos both repress hunchback and caudal.
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What represses hunchback and where is found in an early embryo?
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Hunchback is found in the anterior region and is thus repressed by nanos.
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What represses caudal and where is it found in an early embryo?
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Caudal is foud in the posterior rgion and thus is repressed by bicoid.
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What are bicoid target genes and how does bicoid control them?
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Gap genes; they are controlled by the varying concentration of bicoid.
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What can occur when the expression of two gap genes overlap?
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A third gap gene can be activated.
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What is the order of gap gene expression from anterior to posterior?
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Giant, Hunchback, Kruppel, Knirps, Giant, and Hunchback
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What genes do each of the gap genes repress?
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Their posterior neighbor (Giant represses hunchback wich represses kruppel, …).
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What does the distribution of gap genes dictate?
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The expression of pair rule genes.
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What activates pair rule genes and how so?
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Gap gene regulation activates enhancers which activates pair rule genes.
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What activates the even-skipped gene?
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Biccoid and hunchback
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What represses the even-skipped gene?
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Giant and Kruppel
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What are the secondary pair rule genes?
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fushi tarazu, sloppy-paired, odd-skipped
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What regulates fushi tarazu?
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Primary pair rule genes.
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What are the primary pair rule genes?
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Hairy, even-skipped, and runt
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What gene is expressed on the anterior end of each parasegment?
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Engrailed
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What activates the engrailed gene?
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High levels of even-skipped and fushi tarazu
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What represses the engrailed gene?
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High levels of odd-skipped, runt, or sloppy-paired
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What gene is expressed on the posterior end of each parasegment?
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Wingless
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What activates the wingless gene?
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Low levels of even-skipped and fushi tarazu but high level of sloppy-paired
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What does transcription of engrailed and hedgehog induce?
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Transcription of wingless
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What does transcription of wingless induce?
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Transcription of engrailed
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What is the signaling pathway by which wingless induces transcription of engrailed?
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wnt signaling pathway (wingless binds to frizzled, activates dsh which represses GSK3, GSK3 traditionally breaks down B-catenin, but it is inhibited so B-catenin activates transcription of engrailed.
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What is the signaling pathway by which engrailed induces transcription of wingless?
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Hedgehog (transcribed with engrailed) binds to patched (receptor), activates the smoothened protein, activates cubitus interruptus, activates transcription of wingless.
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What can a homeotic gene do?
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Homeotic genes determine the identity of a segment, moving them to another location can transform the identity of that segment.
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What is the phenotype of a antennapedia mutant?
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An extra set of legs grows from the antenna region.
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What is the phenotype of an ultrabithorax mutant?
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An extra set of wings in the region where it is overexpressed.
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Where is antennapedia found in the WT?
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In the T2 region.
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Where is ultrabithorax found in the WT?
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In the T3 and 1st abdominal segment.
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How is lateral inhibition used in drosophila?
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Signal originates from neuroblasts which inhibits neighbors, forcing them to remain epidermal cells.
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In mammals, what sets up the anterior-posterior axis?
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Gradients of BMP, Wnts, and FGFs
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In mammals, what organizer synonymous structure does not induce head formation?
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The node.
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What two compounds pattern the anterior-posterior axis?
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Retinoic acid and FGFs
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In the first phase of somite differentiation what is controlling the somite?
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The "clock" or notch-delta signaling.
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What occurs in phase two of somite differentiation?
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The cell fate is determined. Anterior-posterior polarity is established
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What occurs in phase three of somite differentiation?
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Maturation, gene expression patterns become fixed.
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What is the identity of somites regulated by?
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HOX genes
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What gene determines which segment will become the 12th and 13th rib and how?
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Hox 3.1 acts as a transcription factor for genes that are specific for the formation of the 12th and 13th rib.
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What structures controll somite cell determination?
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Surface ectoderm and the notochord.
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What are the steps by which a mouse can be made homozygous for an inserted gene?
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The chimeric mouse is mated with a WT mouse. Their heterozygous offspring which are all of the same color (usually a mixture of the WT and the Chimeric parents) are then mated. The progeny are then homozygous transgenic, homozgous WT, and heterozygous. A homozygous transgenic mouse has now been created.
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How is a knockout mouse created?
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The desired gene for knockout is placed in a plasmid then disrupted with a gene for neomycin resistance. This is then added to a mixture of ES cells. By homologous recombination, the gene from the plasmid that has been knocked out will be inserted into the DNA of the ES cells. Cells that have taken up the gene are then selected by their neomycin resistence. These cells are injected into a host blastocyst, forming chimeric offspring. Selective mating is used to select for homozygous transgenic offspring.
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How many cells are found in C. elegans?
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959
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What are are the only lineages which arise from a single founder cell?
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gut and germ
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What is the pathway by which Ced-9 causes cell death?
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Ced-9 inhibits Ced-4 (adapter) which activates Ced-3 (protease)
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What determines cell fate of the germ cell precursors?
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asymmetric segregation of P granules
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What is the germ cell precursor?
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The P4 cell
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What is the intestinal cell precursor?
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The E cell
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Prior to sperm entry where is PAR-3 found?
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The cortical cytoplasm
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After sperm entry where is PAR-3 found and what has replaced it?
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PAR-3 is still found in the cortical cytoplasm, but only on the anterior end. PAR-2 has replaced in on the posterior end (near sperm entry site).
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Prior to sperm entry, where is MEX-5 found?
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The internal cytoplasm
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After sperm entry, where is MEX-5 found?
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MEX-5 is found almost entirely on the anterior side.
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What occurs in a cell-type selection mutation?
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A different type of cell is formed.
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What occurs in a division asymmetry mutation?
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A cell branch is replaced by another.
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What occurs in a mother-daughter difference mutation?
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Differentiation restarts.
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What occurs if a P cell is not present for AB cell differentiation and why?
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The AB cell will not form all of the expected lineage cells because signals from the P cell are needed.
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Describe the lineage starting with the P1 cell.
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[P1 = P2 and EMS] [EMS = MS and E; P2 = P3 and C]
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What induces a EMS cell to form an E cell and a MS cell?
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The P2 cell.
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How does the signal from the P2 cell interact with the EMS cell?
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Via the Wnt signaling pathway.
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If there is no signal from the P2 cell or the Wnt pathway is deffective, what occurs?
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Two MS cells will be formed.
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What surrounds the Anchor cell?
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The gonad
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How are the vulva precursor cells labeled?
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P3.p - P8.p
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What occurs if the anchor cell is destroyed?
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No vulva forms.
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What occurs if the gonad is destroyed.
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The vulva forms.
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Cell ablation studies regarding the vulva show what?
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A signal from the anchor cell is necessary for formation of the vulva.
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How are the fates of VPCs determined?
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The fate of VPCs is determined by the cell's distance from the anchor.
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What type of cell is formed if the signal from the anchor cell is blocked?
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All the VPCs become 3°
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What are the two steps by which the vulva is formed?
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The middle three VPCs receive the signal from the anchor. The central cell then sends inhibitory signals to the neighboring cells. This ensures that only one 1° cell is formed.
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How is a multivulval mutant formed?
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The inhibitory signal from the 1° cell is not present/blocked forming multiple 1° cells.
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What is the initial signal from the anchor cell called?
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Lin-3
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What is the signal from the 1° to the adjacent cells called?
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The signal is unknown, but it activates Lin-12
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What type of signal is Lin-3 similar to?
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FGF which activates the RTK signaling pathway.
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Lin-12 is similar to what kind of receptor?
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The transmembrance Notch protein from the Notch-Delta signaling pathway.
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What occurs when Lin-12 is activated?
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microRNA is produced and blocks the expression of genes that are expressed in 1° cells.
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What is used to intially specify the anchor cell?
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Lin-12
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What is characteristic of the anchor cell during formation?
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It has the most Lag-2 (delta).
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When are germs cells in plants created?
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Germ cells in plants are not set aside early in development, but are formed when environmental conditions favor reproduction.
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How are arabidopsis seeds mutagenized?
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Using EMS (ethylmethane sulfonate)
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How are mutants discovered?
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Mutagenize seeds, grow M1 plant, allow to self fertilize, grom M2 and scan for mutants.
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What is agrobacteria used for?
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It is used to introduce genes into the genomes of plants.
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How are transgenic plants selected for?
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When a gene is inserted into the agro bacteria plasmid, a gene for kanamycim resistence is also inserted. After infected, the plant is grown on kanamycin, causing only transgenic plants to grow.
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Where are new structures formed throughout the life of arabidopsis?
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The root and shoot meristems.
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What are meristems?
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Clusters of cells that allow the basic pattern of a plant (established during ebryogenesis) to be reiterated after germination.
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What cells are in animals are similar to meristems?
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Stem cells.
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Where do apical meristems occur?
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They occur at the growing shoot and root tips.
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What do root apical meristems produce?
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The root cap and daughter cells that produce the three tissues of the root.
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What is the purposed of the root cap?
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The root cap are cells that slough off as the root pushes through the soil.
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What is produced by the shoot apical meristem?
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Stems, leaves, and reproductive structures
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What induces flowering to start?
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Day length, temperature, nutritional status, developmental signals, and hormones.
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What protein expression is driven by clock genes?
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Constans (CO) mRNA
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What protein is regulated by light?
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Constans (CO)
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What type of light breaks down Constans?
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Morning Light
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What type of light stabilizes Constans?
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Evening light
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What is the difference between morning and evening light?
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They are of different wavelengths
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What does constans activate?
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Flowering Locus T (FT) expression
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What hormone can induce flowering?
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Gibberellic acid
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What genes encode for flower meristem identity?
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Leafy, Apetela 1, Cauliflower
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What genes encode for flower organ identity?
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Apetala1, Apetala2, Apetala3, Pistillata, Agamous
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What is the phenotype of an Apetala1 mutatant?
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Mutant has flowers, but no sepals or petals.
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What is the phenotype of an Apetala1 / Cauliflower double mutant?
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Lacks floral identity, appears like cauliflower
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What is the phenotype of a Leafy mutant?
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Has abnormal flowers with no stamen or petals.
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What is the phenotype of a Leafy /Apetala1 double mutant?
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All flowers are converted into leafy shoots.
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What does the first whorl form in arabidopsis?
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Sepal
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What does the second whorl form in arabidopsis?
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Petal
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What does the third whorl form in arabidopsis?
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Stamen
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What does the fourth whorl form in arabidopsis?
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Carpel
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What genes are need to form the sepals?
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A
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What genes are need to form the petals
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A+B
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What genes are need to form the stamens?
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B+C
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What genes are need to form the carpels?
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C
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What are the A genes?
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Apetala1 and Apetala2
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What are the B genes?
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Pistillata and Apetala3
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What are the C genes?
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Agamous
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What kind of transcription factors are the A,B, and C genes?
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MADS-domain
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What is unique about the interaction between the A and C genes?
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They do not overlap each other. If one is mutant, the other takes over.
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How can a gain of function plant be created?
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Add the promoter of another gene to the coding region of the desired gain of function gene. Adding the promoter of an A gene to the coding region of a C gene will cause Agamous to be produced in the sepals and form carpels.
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What occurs in ectopic B and C activity?
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All stamens are formed.
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What occurs in ectopic A and B activity in a C mutant?
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All petals are formed
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What occurs when C is expressed ectopically?
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Sepals are converted into carpels (fruit)
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What occurs when B is expressed ectopically?
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Only petals and staems would be formed.
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What gene maintains meristem identity?
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WUSCHEL (a homeobox gene)
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What gene inhibits WUSCHEL?
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CLV3
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What hormone initiates organi initiation?
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Auxin
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What happns in an A,B,C mutant?
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All the organs become leaves.
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What gene is required for transformation of a leaf into a flower?
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Sepallata
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