Nocodazole is a potent inhibitor of microtubule polymerization, which is required for formation of the mitotic spindle. By treating a population of mammalian cells with nocodazole for a time and then washing it out of the medium, we can synchronize the cell population. In the presence of nocodazole, where in the cell cycle do you expect the cells to accumulate? What mechanism do think is responsible for stopping cell-cycle progression when cells are treated with nocodazole? you

By what molecular pathway does loss of cell cycle regulation in an organism lead to cancer? What genetic changes can cooperate to accomplish the cancer cell’s escape from the normal balance of cell growth?

To identify genes controlling the cell cycle in budding yeast, a genetic screen was carried out. In this screen, haploid yeast cells were exposed to a DNA damaging agent to introduce random mutations in the genome. By culturing cells at an elevated temperature (e.g. 37 degrees), where many mutated genes lose their function, scientists identified yeast mutants that showed growth defects and arrest at specific stages of the cell cycle (e.g. in mitosis with large buds). In this screen, mutants of the cyclin-dependent kinase were identified, but not mutants of cyclins. Explain the reason for this outcome.

Human cells are highly resistant to transformation. Experiments have shown that 5 regulatory circuits (pathways) have to be altered before human cells can grow as tumor cells in immunocompromised mice. State each of these circuits. Explain how the alteration of the protein of that particular circuit leads to uncontrolled growth.        the mitogenic signaling pathway controlled by Ras. the cell cycle checkpoint controlled by pRb. the alarm pathway controlled by p53. the telomere maintenance pathway controlled by hTERT. the signaling pathways are controlled by protein phosphatase 2A, which modulates the activity of the mTOR, Myc, β-catenin, and PKB/ Akt signaling proteins.

When the gene encoding a certain cellular kinase is deleted, the resulting mutant cells arrest in the cell cycle and do not divide. These mutants can be rescued when a gene encoding an N-terminal GFP fusion of the protein is expressed, but not when a gene encoding a C-terminal GFP fusion is expressed. Which fusion protein is appropriate to use in studying cellular localization and activity? Explain why.

BPA is a chemical compound that has historically been used in themanufacture of plastic products. However, cells often mistake BPAcompounds for hormones that accelerate the cell cycle. Because ofthis, BPA is associated with an increased risk of certain cancers. Question: Why do you think that very small concentrations of BPA mighthave a large effect on the cell?

In a dividing cell, the duplicated sets of chromosomes move along microtubules to opposite ends of the cell. How would you use an inhibitor to show that microtubules are essential for chromosome separation?  What control treatment(s) would you use? What kind of cell junctions would you expect to find, and why, in a small animal where a chemical signal passes rapidly through cells to go from the head to the tail?

Explain Cyclin-dependent kinases (CDKs) control the cell cycle by phosphorylating other proteins?

Which of the following need to be expressed to get past the G1 checkpoint and why? Select one: a. All the answers are correct and needed to progress the cell past the G1 checkpoint by expressing the enzymes necessary for DNA replication. Once these proteins are all expressed, the cell has moved past G1 into S phase. b. Primase because this enzyme is needed for DNA replication moving the cell from G1 to S. c. Cyclins because the accumulation of specific cyclins will turn on CDKs needed to turn on gene expression for proteins involved in DNA replication, moving the cell from G1 to S. d. DNA helicase because this protein is needed for DNA replication (part of S phase). So expression will help progress the cell from G1 to S.

Cyclins and cyclin-dependent kinases regulate progression through the cell cycle. Which of the following determines progression beyond the restriction point in G1? Select one: a. The presence of cyclin and Cdk. O b. The presence of cyclin. c. Phosphorylation of RB by Cdk. d. The presence of external signals from growth factors. e. The absence of cyclin.