Chapter 19 Cancer and Regulation of the Cell Cycle1) Mutant versions of genes that are normally involved in promoting the cell cycle are known as ________.A) tumor suppressorsB) proto-oncogenesC) oncogenesD) malignant genesE) attenuatorsAnswer: CSection: 19.42) What is the name of the protein that combines with cyclins to exert local control of the cell cycle?A) cyclin-dependent kinaseB) phosphataseC) ATPaseD) integraseE) hexokinaseAnswer: ASection: 19.33) The retinoblastoma protein (pRB), like p53, serves as a(n) ________ in regulating the cell cycle. A) tumor suppressorB) tumor enhancerC) up regulatorD) oncogeneE) pseudooncogeneAnswer: ASection: 19.44) In sporadic cases of retinoblastoma, how many gene mutations are thought to be necessary in the same cell for a tumor to develop?A) oneB) twoC) fourD) sixE) insufficient information to answer this questionAnswer: BSection: 19.4, 19.61Copyright © 2012 Pearson Education, Inc.5) What is the name of the protein that appears to regulate the entry of cells into an S phase? Thisprotein is also known as the "guardian of the genome."A) p34B) p102C) cyclinD) p53E) phosphokinaseAnswer: DSection: 19.46) A protein that functions as a cell-cycle regulator causes cell death (apoptosis) under high sunlight exposure. What is the symbol given to this protein?A) p34B) p102C) cyclinD) p53E) phosphokinaseAnswer: DSection: 19.37) Which of the following three general mechanisms appear to be involved in the conversion of proto-oncogenes to oncogenes?A) point mutations, translocations, overexpressionB) inversions, translocations, methylationC) familial, sporadic, phosphorylationD) transdetermination, mutation, allosteric interactionsE) suppression, tabulation, projectionAnswer: ASection: 19.28) Which process, other than classical mutation, has recently been found to alter gene expression,as in the expression of CD82 and other metastasis-suppressor genes?A) epigenesisB) tumorigenesisC) metagenesisD) mutational aberrationE) complex couplingAnswer: ASection: 19.22Copyright © 2012 Pearson Education, Inc.9) Driver mutations provide a growth advantage to a tumor cell. Which type of mutation is known to accumulate in cancer cells but has no direct contribution to the cancer phenotype?A) alteration mutationsB) passenger mutationsC) carrier mutationsD) indirect mutationsE) insignificant mutationsAnswer: BSection: 19.110) Provide a definition of cancer at the genetic level.Answer: Cancer is a genetic disorder that can result from mutation of a given gene or genes, which may produce a defective gene product or a change in the timing or amount of gene expression. Such mutations alter cell-cycle control. Some cancers show familial distributions.Section: 19.111) Provide a definition of cancer at the anatomical level.Answer: Cancer is the uncontrolled proliferation of cells and the ability of cells to metastasize ormigrate to other sites to form secondary growths.Section: 19.112) Describe the general relationship that may exist between mutations and cancer.Answer: Control of the cell cycle is dependent on a variety of gene-produced proteins such as kinases and cyclins and related factors. Mutations in genes that encode these proteins may disrupt normal cell-cycle control. The G1 checkpoint is altered in some forms of cancer, and mutant cyclins have been shown to be related to a gene product that is overexpressed in some forms of leukemia. Nonmutant genes often suppress the formation of cancer by exerting control over the cell cycle. When mutant, such control may be lost.Section: 19.413) Describe two classes of proteins known to be involved in the regulation of the cell cycle.Answer: Protein kinases selectively phosphorylate target proteins. When complexed with cyclins, critical points of the cell cycle are controlled.Section: 19.314) Describe the major cellular and molecular events that mark the entry of mitosis from G2.Answer: condensation of chromatin to form chromosomes, breakdown of the nuclear membrane,alterations in the cytoskeleton, formation of an active CDK1/cyclin B complex.Section: 19.215) What is retinoblastoma, and what is its supposed genetic basis?Answer: Retinoblastoma is cancer of the retinal cells of the eye. A familial form is known (about40 percent of all cases), which is caused by a dominant gene. It occurs in a frequency of about 1/17,000, usually appearing at 1 to 3 years of age. A second form of retinoblastoma is not familial (60 percent of all cases), develops later in life, and usually involves only one eye. Two mutations are thought to be required for the disease to occur.Section: 19.43Copyright © 2012 Pearson Education, Inc.16) What is a tumor-suppressor gene? What are oncogenes? What is the normal (nonmutant) cellular version of an oncogene called?Answer: A tumor-suppressor gene is a gene whose normal function is to suppress cell division. When mutant, cell division control is lost and a cancer may form. Oncogenes are genes that induce or maintain uncontrolled cellular proliferation associated with cancer. The normal cellularversion of an oncogene is called a proto-oncogene.Section: 19.417) Describe the cellular and molecular function of the ras gene family and the consequences of mutations in ras.Answer: The ras gene family encodes a protein of 189 amino acids, which is involved with signal transduction in the cell membrane. Point mutations may cause changes in function that promote abnormal signaling, thus stimulating uncontrolled cell growth.Section: 19.418) Describe three genetic mechanisms whereby proto-oncogenes can become overexpressed.Answer: They may acquire a new promoter, upstream regulatory signals, or additional copies (amplification).Section: 19.419) Chronic myelogenous leukemia appears to be associated with a chromosomal rearrangement.How is a chromosomal rearrangement responsible for this disease?Answer: Joining of chromosomes 9 and 22 through translocation generates a hybrid gene bcr/c-abl that produces a protein that is inappropriately active and causes the disease.Section: 19.220) What is the name of a normal gene that serves to promote cellular division?Answer: proto-oncogeneSection: 19.421) List three general categories of genetic changes that lead to the formation of oncogenes.Answer: point mutations, translocations, overexpressionSection: 19.422) What is the difference between a tumor-suppressor gene and a proto-oncogene?Answer: Tumor-suppressor genes act to restrict