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Terms in this set (13)
What is the central question that developmental biologists want to address?
how do single cells turn into a multicellular living organism
What are histones? Why are they important?
histones are a main component of chromatin (wrap around). they are important for minimizing the space DNA takes up. Histones can also be modified to allow access to genes (transcription)
What is a syncytial blastoderm in drosophila?
A syntium in Drosphila i a cell with multiple nuclei all sharing a common cytoplasm. A syncytial blastoderm is when the synctium's nuclei separate on the surface with barriers between them.
What are caderins?
Cadherins are used to attach cells together. They are essential in cell-to-cell communication
On which residues does DNA methylation occur?
DNA methylation occurs on CpG regions. Low CpG region are methylated in their default state and used to repress transcription.
Describe the difference between an enhancer and silencer
Enhancers are used to promote RNA polymerase to bind to the promoter and used to regulate the amount of gene product made. Silencers are used to repress transcription levels by inhibiting polymerase from binding to the promotor
What are morphogen gradients? How do they work? Give one example
Morphogen gradients are concentrations of chemicals that determine cell differentiation. One example is the Bicoid/Nanos morphogen gradient. Bicoid is the chemical that is at higher concentrations in the anterior and represses the caudal morphogen. Nanos is the chemical, which is at higher concentration in the posterior region and prevents Hutchback expression. The differing concentrations of these morphogens determines which axis is on either side and differing cell differentiation
Explains what happens in a bicoid-deficient Drosophila embryo. Also explain what happens if bitcoin mRNA is added at the posterior end of an early wild-type Drosophila embryo
A bitcoin-deficient embryo would be unable to differentiate between the anterior and posterior ends, resulting in no head formation. Without the presence of Bicoid, caudal is not repressed in the anterior portion of the embryo. If bitcoin-mRNA is added at the posterior end of the embryo then both bitcoin and Nanos mRNA would be expressed and the embryo would not be formed correctly, resulting in 2 heads.
Describe one proof that nuclear genes are not lost during cell differentiation
One proof is Dolly the sheep. A somatic cell was fused with an egg cell and was still able to form an embryo. In theory, the two cells would not have been successful in making an embryo if they carried different genes. Cell differentiation allows some genes to be expressed and some repressed. However, the same/all genes are in each cell and have the potential of being expressed.
What does competence mean in reference to receiving a cell signal? What does a cell need in order to be competent to receive a Hedgehog signal in Drosophila?
Competence is the cell's ability to receive a signal (ligand) from another cell and generate a response. In Drosphila, in order to be competent to receive a Hedgehog signal, the responding cell needs to have corresponding receptors on its surface in order to generate the appropriate response from the paracrine pathway. Also the cell needs the signaling pathways necessary. For hedgehog, it is smoothened Li.
Where are the Hedgehog and wingless/wnt proteins synthesized in the cell? How are these proteins modified and why are these modifications important? Give an example of the importance of these modifications
Hedgehog and Wnt proteins are synthesized in the ER. They undergo lipid modifications, transplant, and secretions. One example is cyclopodia and its deficiency in lipid modification.
4 maternal protein gradients seen in the early embryo of drosophila
**Bicoid and hutchback are greatest in anterior
**Nanos and Caudal are greatest in the posterior
paracrine and juxacrine signaling pathways
Juxacrine signaling is used for cell to cell communication on adjacent cells. Paracrine signaling is used for short distance cell communication. In juxacrine signaling, the ligand is transported to an adjacent cell and binds to a nearby receptor on the adjacent molecule. In paracrine signaling, the ligand is released and travels a short distance to a receptor on the receiving cell. In both pathways, if a cell has the corresponding receptor for the released ligands, its generates a response.
Examples: Wnt/ frizzled, Delta/Notch
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