Chapter 11 Learning Curve

Recall the experiments of Peyton Rous and his colleagues. If he had found that filtered cancer cell extract could not cause cancer when injected into healthy animals, what could he have deduced?

ALL ARE CORRECT. An intact cancer cell is necessary to cause cancer. A large protein may cause cancer. Cancer may be caused by bacteria.

How would the loss of p53 activity affect a cell?

ALL ARE CORRECT. DNA damage could accumulate. CDK activity would not be appropriately regulated. The G1 /S checkpoint would not be functional.

Cell division is regulated by:

ALL ARE CORRECT. signals about the nutritional status of the cell. growth factor signals. signals that indicate that DNA has been replicated. signals that indicate that the cell has reached a sufficient size.

Which of the answer choices is true regarding CDKs?

The levels of CDKs change with the cell cycle.

A researcher is evaluating the expression of p53 in cells she is culturing in the laboratory. She notices that in a small group of cells, high levels of phosphorylated p53 occur in the nuclei. What can she deduce about these cells?

These cells likely contain damaged DNA.

How do new cyclin proteins appear in the cytoplasm?

They are made through protein synthesis.

How do CDKs promote cell division?

They phosphorylate proteins that allow passage through cell cycle checkpoints.

What type of protein is being activated by the G1 /S cyclin-CDK complex to promote the expression of histone genes?

a transcription factor

An early observation in the study of the development of sea urchin embryos was that there were several enzymes that became active and then inactive in synchrony with the pattern of rapidly repeating cell divisions. These enzymes had a common characteristic in that they phosphorylate (add phosphate groups to) other proteins. Furthermore, they are only active when bound to another protein—ones that vary in abundance at specific times during the cell cycle. These enzymes are:

cyclin dependent kinases.

A malignant cancer differs from a benign tumor in that:

malignant cancers invade surrounding tissue and benign cancers do not.

The assembly of what cytoskeletal structures are initiated by the M cyclin-CDK complex?

microtubules

One of the important cell cycle checkpoints occurs during M phase. It inhibits progression to anaphase until all of the chromosome kinetochores are correctly attached to microtubules of the spindle apparatus. If anaphase of mitosis occurred when the kinetochore microtubule connected to only one of the two spindle poles but not the other, what could result?

nondisjunction

What type of gene is c-src (cellular-src)?

proto-oncogene

Several years ago, a man noticed a small mole on his wrist. Years later, the mole grew in size and the man was diagnosed as having metastatic melanoma. This was likely the result of:

several mutations affecting proto-oncogenes and/or tumor suppressor genes.

T or F: All cancers are caused by viruses.

False

Which statement regarding tumor suppressors are true?

Mutations affecting tumor suppressors can contribute to the development of cancers.

A woman has her genome sequenced and finds that she carries a mutation in p53. Will she develop cancer?

Possibly; this mutation is likely to predispose her to developing certain types of cancer.