Pollev

You pulse label cells in culture briefly with [H3] thymidine. The cells are at all different stages of cell cycle (unsynchronized). You know that your cells complete the entire cell cycle in 24 hours, and that the S phase is 6 hours and M-phase is 2 hours.

Question 1: what fraction of cells in M phase will be labeled after you wash out the pulse and wait a few minutes?

none (0%)

You pulse label cells in culture briefly with [H3] thymidine. The cells are at all different stages of cell cycle (unsynchronized). you know that your cells complete the entire cell cycle in 24 hours, and that the S phase is 6 hours and M-phase is 2 hours.

Question 2: after several different chase (no label) lengths - 8, 9, or 10 hours -, you only find labeled cells in M when you wait 10 hours. what do you conclude?

the G2 phase is between 9-10 hours long

If a cell in the G2 phase is fused with a cell in the M phase

the G2 nucleus will enter the M phase

Cyclin concentrations are highest during which periods of the cell cycle?

late G2 and early M

Which of the following statements is NOT true regarding the wee1 gene?

The normal wee1 gene product causes the cells containing it to be smaller, hence the name "wee."

What enzyme below does diacylglycerol (DAG) recruit and activate?

protein kinase C

What role do activated steroid receptors play in the cell?

ligand-regulated transcription factors

Which of the following has NOT been identified as a second messenger?

ATP

If you break liver cells by homogenization, separate the broken cell membranes (particulate) from the cytoplasm (soluble), and add epinephrine to the soluble portion, the result will be:

no change in glycogen phosphorylase activity

Sometimes an enzyme is activated by a receptor and brings about the cellular response by generating a second messenger. Such an enzyme is called a(n)

effector

Phosphorylation of a protein can change its behavior in all of these ways EXCEPT:

it can initiate protein synthesis

Epinephrine binds to the same type of receptors in liver and smooth muscle cells. Yet liver cells break down glycogen and smooth muscle cells relax. How can the same hormone produce such different responses?

The same hormone and its second messengers activate different intracellular proteins with different functions.

Which statement below is a correct statement about the abilities of normal cells and cancer cells to grow and divide when cultured under conditions favorable for cell proliferation?

Malignant and normal cells grow and divide at similar rates

Cancer is not characterized by

controllable cell proliferation

Which of the followings incorrectly describes tumor suppressor genes?

Any mutation in tumor-suppressor genes can lead to cancer

What are a variety of genes that have the potential to subvert the cell's own activities and push it to the malignant state. They encode proteins that have various functions in a cell's normal activities and can be converted to what

Proto-oncogenes, oncogenes

You are studying a human cell cycle protein commonly mutated in cancer cells. You express this protein in yeast and find that the cells start to divide faster. You decide to use this system for screen for a drug that may inhibit the activity of this protein. Of the following scenarios, which one suggests you have identified an inhibitor of the human protein?

You identify a drug that causes yeast cells expressing the protein to grow normally

Cancer is a genetic disease in that it can be traced to alterations within specific genes, but, in most cases, it is not an inherited disease. Why is that the case?

The genetic alterations in most cancers arise mostly in the DNA of somatic cells during the lifetime of the affected individual.

Death by apoptosis is a neat, orderly process characterized by

All of these answers are correct

Which of the following statements correctly describes proto-oncogenes and/or oncogenes?

Oncogenes are converted from proto-oncogenes by mutation or other means that change the gene expression levels or functions

Below are some steps in the signal transduction cascade that occur after an odor binds

to a GPCR. Read the list, then choose the answer that has the correct sequence of the

steps after the heterotrimeric G-protein has associated with the ligand-bound receptor.

I. adenylyl cyclase produces the second messenger cAMP

II. heterotrimeric G protein reassembles

III. Galpha releases GDP, binds GTP

IV. Galpha hydrolyzes GTP (shutting off adenylyl cyclase)

V. Galpha dissociates from beta and gamma subunits. Galpha (with GTP) binds and activates effector, adenylyl cyclase

III, V, I, IV, II

With respect to signaling mediated by Protein Kinase A (PKA), which of the following is NOT true?

PKA cleaves PIP2 to generate IP3 and diacylglycerol

Which of the following does NOT contribute to the movement of chromosomes apart during anaphase?

microtubule addition at the plus ends of astral spindle microtubules

You have a culture of mammalian cells that you treat with the drug nocodazole. At what cell cycle stage will the cells arrest?

the spindle assembly checkpoint (prometaphase)

A paper published recently described a new type of "bacterial microtubules (bMTs)". The authors found that bMTs are comprised of heterodimers of tubulin A and B molecules and polymerize in the presence of ATP. bMTs have 13 protofilaments arranged in a hollow tube. Which of these characteristics of bMTs makes them different from eukaryotic microtubules?

using ATP instead of GTP

Which of the following conditions describes one that is clearly energetically favorable for an ion to move through a open, gated ion channel into a cell

the ion concentration is higher outside the cell than inside AND the charge is opposite just inside the cell (at least locally)

Which of the following statements about cell membranes is FALSE?

The membrane-bound organelles within a single cell all share the same lipid and membrane protein composition (by percent) as that cell's plasma membrane.