Biology unit 4

4. What is the expected percent chance in the DNA content of a typical eukaryotic cell...?

+100%

11. The diagram above illustrates feedback control as exerted by the hormone thyroxine...

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

2. Cancer can result from a variety of different mutational events. Which of the following is LEAST....

A defect in a cell-cycle checkpoint prevents a cell from entering S phase.

20. ....When the components in pathway II are sequentially activated, downstream signaling by the G protein is inhibited. Based on the model, which of the following mutations is most likely to result in a cell that will generate a cancerous tumor?

A mutation in the gene encoding G-PIP that results in a nonfunctional protein.

12. Which of the following is most likely to reduce the binding of active ligand to its receptor?

A mutation in the receptor gene that causes a substitution of a charged amino acid for a nonpolar amino acid in the ligand binding site of the receptor.

19. Based on the model, which of the following best describes an outcome of B cell activation?

Activated B cells differentiate into plasma cells and memory cells.

18. Which of the following predictions about the activity of platelets best describes a positive feedback mechanism?

Activated platelets release chemicals that activate more platelets.

14. A dog is following the scent of a jack rabbit. Which of the following accurately describes how the dog's brain integrates information for smell?

Chemoreceptor cells in the nasal cavity send impulses to the appropriate area of the brain.

6. Which of the following presents a correct interpretation of the changes in chromosome number depicted in figure 1?

Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated...

8. If chemical signals in the cytoplasm control the progression of a cell to the M phase of the cell cycle, then fusion of a cell in G1 with a cell in early M phase would most likely result in the

Condensation of chromatin in preparation of nuclear division in both cells

7. DNA replication occurs

During the S phase of the cell cycle

15. ....steps in the process whereby epinephrine stimulates glycogen breakdown?

Epinephrine binds to a cell-surface receptor; the activated receptor stimulates production of the second messenger, cAMP

1. Many human cells can be simulated to divide by hormone-like growth factors that bind to receptor proteins (R) on the plasma membrane...

Growth-Factor signaling can trigger mitosis in cells that are in direct contact with other cells.

3. ...the effect of certain genetic mutations on mitosis in tropical fruit fly embryos. They determined the percentage of cells in each of four phases of mitosis as shown in figure 1....

In mutant 3 cells, more time is spent in prophase/pro metaphase than in the later stages of mitosis.

9. A researcher examining a root tip observed a plant cell with condensed sister chromatids...

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

17. The p53 protein regulates a cellular response to DNA damage. Based on the diagram above, which of the following best describes the role of p53 in the response to DNA damage?

Phosphorylated p53 stimulates transcription of p21, and the resulting p21 protein suppresses cell division until the DNA damage is repaired

16. Based on the information presented, which of the following will also occur in response to steroid signaling?

Production of a specific mRNA will increase as a result of the binding of the hormone-receptor complex to the DNA

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

Replicated chromosomes line up on the equatorial plate.

10. Which of the following best describes how the amount of DNA in the cell changes during M phase?

The amount of DNA is halved as the cell divides into two daughter cells

13. Which of the following can most likely be concluded about the TSH-thyroxin loop?

The feedback mechanism works remain relatively constant levels of thyroxin throughout tissue targets.