Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Chapter 20, Problem 23P
Families with germ-line BRCA1 or BRCA2 loss-of-function mutations usually display Hereditary Breast and Ovarian Cancer (HBOC). The accompanying diagram shows a BRCA2 pedigree.
| a. | BRCA1 and BRCA2 are tumor-suppressor genes; cells homozygous for loss-of-function mutations in either gene can become cancerous due to a loss of DNA repair machinery. Explain why the pedigree shows a dominant inheritance pattern of HBOC. |
| b. | Can you tell from the pedigree diagram whether or not HBOC is completely penetrant? |
| c. | Does HBOC show varying expressivity? |
| d. | Explain your answers to parts (b) and (c) in terms of current models for the origins of cancers. |
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Genetic tests that detect mutations in the BRCA1 and BRCA2 tumor-suppressor genes are widely available. These tests reveal a number of mutations in these genes—mutations that have been linked to familial breast cancer. Assume that a young woman in a suspected breast cancer family takes the BRCA1 and BRCA2 genetic tests and receives negative results. That is, she does not test positive for the mutant alleles of BRCA1 or BRCA2. Can she consider herself free of risk for breast cancer?
Genetic tests that detect mutations in the BRCA1 and BRCA2 oncogenes are widely available. These tests reveal a number of mutations in these genes—mutations that have been linked to familial breast cancer. Assume that a young woman in a suspected breast cancer family takes the BRCA1 and BRCA2 genetic tests and receives negative results. That is, she does not test positive for the mutant alleles of BRCA1 or BRCA2. Can she consider herself free of risk for breast cancer?
There are three broad categories of cancer-related genes: proto-oncogenes, tumor suppressor genes, and DNA stability/repair genes. Define each of these categories and indicate which one you think the RB1 gene belongs to and why.
Chapter 20 Solutions
Genetics: From Genes to Genomes
Ch. 20 - For each of the terms in the left column, choose...Ch. 20 - Characterize the differences between tumor cells...Ch. 20 - Prob. 3PCh. 20 - Prob. 4PCh. 20 - A carcinogenic compound is placed on the skin of...Ch. 20 - You have decided to study genetic factors...Ch. 20 - B cells are specialized blood cells that secrete...Ch. 20 - Molecules outside and inside the cell regulate the...Ch. 20 - Put the following steps in the correct ordered...Ch. 20 - a. Would you expect a cell to continue or to stop...
Ch. 20 - Two different protein complexes called SCF and APC...Ch. 20 - One of the hallmarks of mitotic anaphase is the...Ch. 20 - Concerning the Tools of Genetics Box Analysis of...Ch. 20 - Are genome and karyotype instabilities...Ch. 20 - Prob. 15PCh. 20 - Why dont all loss-of-function mutations that are...Ch. 20 - Chromothripsis is a rare phenomenon, first...Ch. 20 - The chromosome 9/22 translocation associated with...Ch. 20 - A female patient 19 years old, whose symptoms are...Ch. 20 - Prob. 20PCh. 20 - A generic signaling cascade is shown in the...Ch. 20 - Neurofibromatosis type 1 NF1; also known as von...Ch. 20 - Families with germ-line BRCA1 or BRCA2...Ch. 20 - The text explained that retroviruses can cause...Ch. 20 - Hepatocellular carcinoma is the most frequent form...Ch. 20 - Suppose that instead of microarrays, you analyzed...Ch. 20 - Prob. 27PCh. 20 - Glioblastoma multiforme GBM is the most common and...Ch. 20 - a. The legend to Fig. 20.29 identifies which of...Ch. 20 - The website CBioPortal http://www.cbioportal.org...
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- In what category of cancer-related genes is it possible to find inherited variants that are associated with cancer? Why? Group of answer choices 1. Tumor suppressor genes, because genes in this category are very important in the process of developing cancer. 2. Proto-oncogenes, because individuals who carry only one cancer-causing allele will have a wildtype phenotype. 3. Proto-oncogenes, because there are very few genes in this category, so mutations in them are rare. 4. Tumor suppressor genes, because individuals who carry only one cancer-causing allele will have a wildtype phenotype.arrow_forwardd)To cause cancer, proto-oncogenes require (1 or 2)allele(s) to be mutated and therefore are considered (dominant or recessive). The mutation results in a (loss or gain) of function. For each underlined pair, boldface one. e)To cause cancer, tumor suppressor genes require (1 or 2)allele(s) to be mutated and therefore are considered (dominant or recessive). The mutation results in a (loss or gain) of function. For each underlined pair, boldface one.arrow_forwardThe Human papillomavirus (HPV) has been linked to an increased risk of cervical cancer. The HPV E6 and E7 proteins govern the cell via altering cellular proteins. The E6 protein interacts with the tumor suppressor protein p53 and directs its ubiquitin-mediated destruction. Can you elaborate about the P63 gene: its function and if it can be altered/mutated by HPV? If it does, what is the relationship between P53 and P63? Thank you!arrow_forward
- Distinguish between proto-oncogenes and tumor-suppressor genes. To become cancer promoting, do proto-oncogenes and tumor-suppressor genes undergo gain-of-function or loss-of-function mutations? Classify the following genes as proto-oncogenes or tumor-suppressor genes: p53, ras, BCL-2, JUN, MDM2, and p16.arrow_forwardThe propensity to develop retinal cancer can run in pedigrees of certain families. You have learned about the role of the retinoblastoma (Rb) protein in the cell cycle. A heterozygous individual (genotype = Rbm / Rb+) that inherits a mutant allele of the Rb gene (Rbm) as well as a normal allele of the Rb gene (Rb+) is at significant risk for developing cancer of the retina. The best explanation for this is that… A. the Rb(m) allele is dominant to the Rb(+) allele. B. a mutation in the Rb(+) allele can result in a Rb(m) / Rb(m) genotype in certain cells. C. the retina is frequently exposed to UV rays D. the Rb(m) allele directly converts the Rb(+) allele to another Rb(m) allele. E. the cells of the retina carry more than two copies of the Rb genearrow_forwardThere are three broad categories of cancer-related genes: proto-oncogenes, tumor suppressor genes, and DNA repair/stability genes. Distinguish between these three groups, then indicate which you think RB1 belongs to.arrow_forward
- Tumor suppressor genes and oncogenes are implicated in carcinogenesis. However, one can predict whether a gene potentially encodes for a protein that influences carcinogenesis by examining their mutational profile. You sequence the genome of 4 cancers and identify 3 genes of interest. Which of the following genes has the best potential to an oncogene? Tumor 1 Tumor 2 Tumor 3 Tumor 4 Gene A S24F, N465T R33T T345S, G366R P367E, P368Y Gene B S34R, F360I S34R V254I S34E, T67Y Gene C S24F, I322E C255I, E344D S34E, P367Earrow_forward1. a)Proteins that stimulate/promote progression through the cell cycle are encoded by (oncogenes or tumor suppressor genes). Boldface one. b)Proteins that inhibit progression through the cell cycle are encoded by (oncogenes or tumor suppressor genes). Boldface one. c)What is the difference between a proto-oncogene and an oncogene? d)To cause cancer, proto-oncogenes require (1 or 2)allele(s) to be mutated and therefore are considered (dominant or recessive). The mutation results in a (loss or gain) of function. For each underlined pair, boldface one. e)To cause cancer, tumor suppressor genes require (1 or 2)allele(s) to be mutated and therefore are considered (dominant or recessive). The mutation results in a (loss or gain) of function. For each underlined pair, boldface one.arrow_forwardCellular levels of tumor suppressor protein p53 is maintained by a ubiquitin ligase protein, called Mdm2. Over expression of Mdm2 destabilizes p53. Another protein p19ARF inhibits the activity of Mdm2, thus stabilizing p53. Loss of p19ARF function converts normal cells into cancer cells With the above information, which of the following statements are true? Mdm2 is a tumor suppressor gene but p19ARF is an oncogene Both Mdm2 & P19ARF are oncogenes Both Mdm2 & P19ARF are tumor suppressor genes O Mdm2 is an oncogene but p19ARF is a tumor suppressor genearrow_forward
- Describe the mutational event that produces the MYC oncogene in Burkitt’s lymphoma. Why does the particular mechanism for generating oncogenic MYC result in a lymphoma rather than another type of cancer? Describe another mechanism for generating oncogenic MYC.arrow_forwardDescribe the steps by which the TP53 gene responds to DNA damage and/or cellular stress to promote cell-cycle arrest and apoptosis. Given that TP53 is a recessive gene and is not located on the X chromosome, why would people who inherit just one mutant copy of a recessive tumor-suppressor gene be at higher risk of developing cancer than those without the recessive gene?arrow_forwardExplain why mutations in tumor suppressor genes are recessive (both copies of the gene must be defective for the regulation of cell division to be defective), whereas mutations in oncogenes are dominant.arrow_forward
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