study

The diagram above illustrates feedback control as exerted by the hormone thyroxine. Following surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the following best explains this increase?

A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary, leading to increased TSH secretion.

18. Figure 1. Diagram of the cell cycle with key checkpointsWhich of the following describes a mutation that would lead to an increase in the frequency of nondisjunction?

A mutation affecting checkpoint 3 proteins that prevents attachment of spindle fibers

5. Type 1 diabetes results from the destruction of insulin-producing cells in the pancreas. Individuals with type 1 diabetes produce insufficient amounts of insulin, a hormone that regulates the concentration of glucose in the blood.Which of the following best explains how treatment with a drug that stimulates the production of insulin receptors on target cells will affect the insulin signaling pathway in an individual with type 1 diabetes?

A. The drug will have little or no effect on the signaling pathway because the receptors will not be activated in the absence of insulin.

8. Damaged tissue releases chemicals that activate platelets and stimulate the formation of blood clots. Which of the following predictions about the activity of platelets best describes a positive feedback mechanism?

Activated platelets release chemicals that activate more platelets.

6. Which of the following best explains the role of apoptosis in remodeling of the forelimb?

B: apoptosis involves the regulated activation of proteins in specific cells of the developing forelimb that leads to the death of those cells.

21. A researcher claims that the epinephrine signaling pathway controls a catabolic process in muscle cells. Which of the following statement best helps justify the researcher's claim?

D. Glycogen phosphorylase catalyzes the conversion of glycogen to glucose-1-phosphate

19. Based on Figure 1, which of the following statements best describes the epinephrine signaling pathway?

In involves enzymes activating other enzymes.

20. Which of the following statements best describes the role of adenylyl cyclase in the epinephrine signaling pathway?

It accelerates the production of a second messenger.

17. Which of the following is true of mitosis?

It is the last phase of interphase

16. Basic on the model of urkaryotic cell cycle regulation show in figure, which of the following is best described the effect of a drug that blocks the production of mitosis cyclin?

The cell would be prevented from entering mitosis, and the cell would stop dividing.

7. Human epidermal growth factor (EGF) is a protein that stimulates cell division and growth by binding to its receptor, human epidermal growth factor receptor 2 (HER2). Certain types of cancer are caused when the overexpression of EGF activates a cell-signaling pathway, leading to uncontrolled cell division. Which of the following best explains how a drug can be used to inhibit tumor growth caused by EGF overexpression?

The drug binds to HER 2, preventing the activation of the signaling pathway.

26. A DNA mutation changes the shape of the extracellular domain of transmembrane receptor protein A produced by the cell. Which of the following predictions is the most likely consequence of the mutation?

The molecule that normally binds to protein A will no longer attach, deactivating the cellular response.

13. cancer can result from a variety of different mutational events. which of the following is least likely to result in the initiation of a cancerous tumor?

a defect in a cell cycle checkpoint prevent a cell from entering the S phase

16 If a dietary change results in an increase in blood calcium concentration above normal levels, which of the following is the most likely effect on calcium homeostasis?

b. Calcitonin levels will rise, thus promoting the deposit of calcium into bones.

11. A researcher examining a root tip observes a plant cell with condensed sister chromatids, kinetochores with attached microtubules, and individual chromosomes that are aligned at the equatorial plate of the cell. Which of the following best describes what the next process will be in the cell?a.) Homologous

b. Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.

10. During mitosis, which of the following normally occurs?

b. replicated chromosomes line up on the equatorial line

13. Most cells that have become transformed into cancer cells have which of the following characteristics when compare to normal, healthy cells?

shorter cell cycle.