polymer that doesn't have memory

what polymer has no memory

Compare and contrast the structure, life cycle, and host cell type of naked and enveloped viruses.

Describe the ionic basis of an action potential and be sure to include the role of channels/gates within the cell membrane and how this relates to a positive feedback homeostatic mechanism.

1. Antibody is prepared to the thr repressor protein isolated from a wild-type strain.  Competetive antibody binding assays show that several times more repressor is present in an extract prepared from the derepressed mutant described above than in an extract prepared from the wild-type strain.  What is your interpretation of these data?
2. The repressor protein requires a pH of 6.1 for optimal binding to its operator in vitro.  If the pH goes above pH 8.0, the repressor is unable to bind.  What amino acid side chains are implicated?  Why is binding reduced in alkaline media?
3. What effect would an increase in pH have on cell transcription of the thr operon? Why?
4. What percentage of the repressor will bind at pH 6.3?  More than 50% or less?  Now calculate.

What disease present with pinkish rash on hands and feet them arms and legs and fever in children

How does the SOS system simultaneously fix damage DNA and increase the mutation rate? How does the SOS system increase the survival of microorganisms?

Put the events of neural signal transmission at the synapse in the order that they occur from first to last.

First to Last

1.Action potential arrives at synaptic terminal from axon.

2.Vesicles in sending neuron fuse with the membrane.

3.Neurotransmitters are released into the synaptic cleft.

4.Neurotransmitters bind to receptor proteins on the receiving cell membrane.

5.Ion channels in the receiving neuron are stimulated to open.

6.Chance of action potential in the receiving cell either increases or decreases.

1. What is meant by genomic equivalence?

Explain an experiment that supports genomic equivalence by providing functional evidence (Hint: think about what is meant by functional evidence or producing dolly the sheep vs. descriptive evidence like labeling a chromosome and determining different cells in an organisms all have the same chromosome structure). Describe the hypothesis, brief methods, results and conclusion reached.

1. What is the overall message of von Baer’s Laws?

2. Why do you think Darwin was intrigued by these laws (hint: think in terms of continuity and evolution)?

2. During the earliest phases of nervous system development, morphological changes occur and result in the formation of a neural tube.

1. What is the molecular mechanism by which the neural tube physically separates from the epidermis? (Hint: think about differential cell-cell adhesion)

2. Define a “lose it” or loss-of-function technique that would allow you to support that the molecular mechanism above occurs.

3. Describe what is meant by epithelial to mesenchymal transition.

4. During early syncytial specification in Drosophila, bicoid  mRNA localizes to the anterior end of the embryo, where it generates a concentration gradient of the Bicoid morphogen responsible for the development of the head. You perform a chromatin IP experiment to identify new genes that are regulated by the Bicoid transcription factor. You discover Bicoid binds very strongly to the regulatory DNA of a kinase, gene H. It is your job to design a series of experiments to determine if gene H actually functions during head formation of Drosophila.

Briefly describe a strategy for each of the following scientific approaches: (i) find it, (ii) lose it, and (ii) move it (that is, (i) correlation, (ii) requirement, and (iii), sufficiency).

5. It is known that specific signaling pathways promote the development of dorsal structures like the brain and spinal cord. A mutation was discovered in zebrafish that resulted in the duplication of the dorsal side of the embryo (i.e. two heads/brains and spinal cords fused with a shared ventral belly). The loss of function mutation was mapped to the gene Axin, that is, Axin gene function is reduced or removed entirely from the embryo.

1. Which signaling pathway would be affected by the Axin mutation?

2. What is likely to be the effect on Axin loss-of-function on the above signaling pathway (increased or decreased signaling)?

3. Using a reporter gene, how would you test the effect of the axin mutation on the above signaling pathway?

6. Ectopic expression of a gene is forced expression outside of the genes normal domain. In Drosophila, the Gal4 system is used to ectopically express genes in specific places and times.

1. Describe a strategy using the Gal4 system in Drosophila to generate an additional set of eyes in place of the antenna (Hint: think in terms of the ectopic expression an eye master regulator in the antenna domain).  

2. Considering the stages of cell commitment, how might you characterize a cell that initially moves towards an antenna cell fate but then becomes persuaded to be an eye cell? (Hint: think of the environment created by the Gal4 expression system and whether this translates to a neutral or non-neutral developmental context).

7. Dnmts are methyltransferases that function by adding a methyl group to the cytosine of DNA.

1. Describe the importance of DNA methylation to cell identity. How does cell identity play a role in development and maintenance of a tissue?  

2. Explain the connection between DNA methyl and histone methylation?

1. What is an organoid and why are they useful to understanding human development and disease.

2. Briefly describe a strategy where you would use a patient-specific organoid to attempt to understand and cure a disease that you are most interested? (Hint: first think about the disease, then harvesting cells, then creating a useful type of organoid from iPS cells).

1. Describe the mechanism of syncytial specification.  

2. How is it possible that a morphogen gradient of a protein transcription factor can transmit a signal inside the cells of a syncytial embryo?

3. How do morphogen gradients come together to specify regions of the syncytial embryo? (Hint: think about levels of morphogens).

1. What is a stem cell niche? How does a stem cell niche regulate stem cell function?

2. Describe one example of a stem cell niche.

1. What human cell types are pluripotent?

2. Why does harvesting the above pluripotent cells create a moral dilemma?

3. What can be done in the lab to avoid the above moral complications?

1. In lineage tracing experiments, embryonic tissues that are labeled can be moved from a donor to the same region of a host. The point is to watch to see what the marked cells ultimately become in the older organism. You are interested in studying the formation of the central nervous system in a frog.

1. Indicating a strategy by which you can label donor cells so they can be visualized at a much later time in development.

2. If you are interested in tracing cells that make their way into the central nervous system, where would you have to transplant those labeled cells in the early embryo.

Select all of the following that are true about a neuron’s function.

1.An action potential occurs if the membrane potential exceeds the threshold potential.

2.A neuron expends no energy while it maintains a resting potential.

3.When the neuron receives a stimulus, sodium ions begin to rush out of the axon.

4.When threshold potential is reached, sodium channels all along the axon open up at once.

5.An axon maintains a positive charge during rest.

6.During the peak of an action potential, more sodium ions are found inside the axon than when it is at resting potential.

7.During an action potential in one section of an axon, sodium channels first open, then delayed potassium channels open and sodium channels close.

Please explain the difference between positive control, positive regulation,negative control and negative regulation pertaining to DNA.

If you exposed an unknown bacteria to four different bacteriophages. Susceptibility of the bacteria will be determined by observing for the production of plaques. Describe how these plaques are formed?

. A female patient has been suffering from continuous diarrhea for a week. The stool had a metal like smell. The patient is a nurse at an Assisted living home. She felt sick a week ago and her symptoms resembled that of one of her own patients. Her symptoms have been worsening to the point she is very sick and had to take time off. 1. What disease does she have? Name the causative agent. 2. How did she become infected with this microbe? Explain the pathogenesis of this disease. 3. What is the virulence factor and how would you treat this disease? 4. What would you advise the patient to do in the future to avoid such illness in particular in her line of work.