Exam 20: Genetics of Cancer

Suppose you are studying a rare spontaneous cancer in cats,which you suspect is retrovirus-induced.What kinds of retroviral insertion could lead to cancer,and what kind of genetic signature would you look for to distinguish between them?

v-onc genes are found in

Small DNA tumor viruses such as SV40 and HPV have viral oncogenes that are not homologs of host cell genes.Some of these novel viral oncogenes make proteins that exert their tumorigenic effect by

In retroviruses,the pol gene product is a(n)

________ play a pivotal role in programmed cell death.

List the ways in which proto-oncogenes may be converted to oncogenes.

Programmed cell death,or apoptosis,is a necessary and useful property of cells.Why is this so?

When oncologists (scientists who study cancer)refer to "transformation," they mean something different from what the word "transformation" signifies when used by biotechnologists.Explain the difference between the two uses of the term in genetics.

The only genes necessary for the retroviral lifecycle are gag and pol.

Metastatic cancer is

BRCA1 is a gene involved in repair of double-stranded DNA breaks.Mutant forms of this gene are linked to a substantial proportion of familial breast cancers.A woman who inherits a certain allele of the gene has about a 60-80% chance of getting breast cancer,as well as an elevated chance of getting ovarian cancer,in her lifetime. a.Why don't a higher percentage of women with the mutation get breast cancer? b.How would the breast cancer inheritance caused by BRCA1 be described in Mendelian terms?

Describe Knudson's two-mutation model: When and where are the mutations posited to occur?

In sporadic (nonhereditary)cancers,mutations occur in ________ cells.

A proto-oncogene that gains function due to amplification,translocation to a more transcriptionally active area of the genome,or a mutation that causes either an increase in function or the suppression of down-regulation,is

Which of the following is not likely to be a tumor suppressor?

People with the genetic disease xeroderma pigmentosum have compromised DNA repair mechanisms,making them extremely sensitive to genetic damage from sunlight.Without taking measures to minimize exposure,these individuals typically succumb to skin cancer in childhood or early adulthood-a demonstration of the mutagenicity of ultraviolet radiation.Yet,deliberate exposure in the form of sunbathing is very popular with some segments of the population.Why do you think this is so,and how might public health professionals raise awareness of the danger in which these people place themselves?

Retroviruses are responsible for which of the following conditions?

Li-Fraumeni syndrome is a rare inherited disease that greatly increases a person's risk of developing several types of cancer.This disease stems from a mutation in the TP53 tumor suppressor gene (Nichols et al.2001.Cancer Epidemiol Biomarkers Prev 10:83-87).In most cases,approximately 95% of the mutations can be detected by sequence analysis of exons 4 through 9.If you isolated and analyzed DNA from a Li-Fraumeni patient,what genotype should you find in DNA isolated from a.normal tissue? b.malignant tissue?

The process of relaying a growth-stimulatory or growth-inhibitory signal in response to an extracellular factor binding at the cell surface is called intercellular signaling.

The terms proto-oncogene and oncogene may give the misleading impression that these are "genes for cancer" that are waiting to be turned on.What are these genes,in terms of normal function,and what name might have been given to them to reflect this function rather than their role in cancer?