Cancer Genetics Overview (PDQ)

Purpose of This PDQ Summary

This PDQ cancer information summary for health professionals provides a framework for understanding the genetic basis of hereditary cancer. This summary is reviewed regularly and updated as necessary by the PDQ Cancer Genetics Editorial Board.

Information about the following is included in this summary:

The PDQ Cancer Genetics summaries contain level-of-evidence designations. These designations are intended to help readers assess the strength of the evidence in relation to specific studies or strategies. A description of how the level of evidence designations are made is described in detail in this summary.

This summary does not provide formal guidelines or recommendations for making health care decisions. Information in this summary should not be used as a basis for reimbursement determinations.


Many of the medical and scientific terms used in this summary are found in the NCI Dictionary of Genetics Terms. When a linked term is clicked, the definition will appear in a separate window.

The etiology of cancer is multifactorial, with genetic, environmental, medical, and lifestyle factors interacting to produce a given malignancy. Knowledge of cancer genetics is rapidly improving our understanding of cancer biology, helping to identify at-risk individuals, furthering the ability to characterize malignancies, establishing treatment tailored to the molecular fingerprint of the disease, and leading to the development of new therapeutic modalities. As a consequence, this expanding knowledge base has implications for all aspects of cancer management, including prevention, screening, and treatment.

Genetic information provides a means to identify people who have an increased risk of cancer. Sources of genetic information include biologic samples of DNA, information derived from a person’s family history of disease, findings from physical examinations, and medical records. DNA-based information can be gathered, stored, and analyzed at any time during an individual’s life span, from before conception to after death. Family history may identify people with a modest to moderately increased risk of cancer or may serve as the first step in the identification of an inherited cancer predisposition that confers a very high lifetime risk of cancer. For an increasing number of diseases, DNA-based testing can be used to identify a specific mutation as the cause of inherited risk and to determine whether family members have inherited the disease-related mutation.

Throughout this summary, the term “mutation” will be used to refer to a change in the usual DNA sequence of a particular gene. Mutations can have harmful, beneficial, neutral, or uncertain effects on health and may be inherited as autosomal dominant, autosomal recessive, or X-linked traits. Mutations that cause serious disability early in life are usually rare because of their adverse effect on life expectancy and reproduction. However, if the mutation is autosomal recessive—that is, if the health effect of the mutation is caused only when two copies (one from each parent) of the mutated gene are inherited—mutation carriers (healthy people carrying one copy of the altered gene) may be relatively common in the general population. "Common" in this context refers, by convention, to a prevalence of 1% or more. Mutations that cause health effects in middle and older age, including several mutations known to cause a predisposition to cancer, may also be relatively common. Many cancer-predisposing traits are inherited in an autosomal dominant fashion, that is, the cancer susceptibility occurs when only one copy of the altered gene is inherited. For autosomal dominant conditions, the term “carrier” is often used in a less formal manner to denote people who have inherited the genetic predisposition conferred by the mutation. Refer to individual PDQ summaries focused on the genetics of specific cancers for detailed information on known cancer-susceptibility syndromes.

Increasingly, the public is turning to the Internet for information related both to familial and genetic susceptibility to cancer and to genetic risk assessment and testing. Direct-to-consumer marketing of genetic testing for hereditary breast and colon cancer is also taking place in some communities. This wider availability of information related to inherited cancer risk may raise concerns among persons previously unaware of the implications inherent in their family histories and may lead some of these individuals to consult their primary care physicians for management advice and recommendations. In many instances, the evaluation and advice will be relatively straightforward for physicians with a basic knowledge of familial cancer. In a subset of patients, the evaluation may be more complex, calling for referral to genetics professionals for further evaluation and counseling.

Correctly recognizing and identifying individuals and families at increased risk of developing cancer is one of countless important roles for primary care and other health care providers. Once identified, these individuals can then be appropriately referred for genetic counseling, risk assessment, consideration of genetic testing, and development of a management plan. When medical and family histories reveal cardinal clues to the presence of an underlying familial or genetic cancer susceptibility disorder (see list below), [1] further evaluation may be warranted. Refer to the PDQ summary on Elements of Cancer Genetics Risk Assessment and Counseling for more information about the components of a genetics cancer risk assessment.

Features of hereditary cancer include the following:

Concluding that an individual is at increased risk of developing cancer may have important, potentially life-saving management implications and may lead to specific interventions aimed at reducing risk (e.g., tamoxifen for breast cancer, colonoscopy for colon cancer, or risk-reducing salpingo-oophorectomy for ovarian cancer). Information about familial cancer risk may also inform a person’s ability to plan for the future (lifestyle and health care decisions, family planning, or other decisions). Genetic information may also provide a direct health benefit by demonstrating the lack of an inherited cancer susceptibility. For example, if a family is known to carry a cancer-predisposing mutation in a particular gene, a family member may experience reduced worry and lower health care costs if his or her genetic test indicates that he or she does not carry the family’s disease-related mutation. Conversely, information about familial cancer risk may have psychological effects or social costs (e.g., worry, guilt, or increased health care costs). Family dynamics also may be affected. For instance, the involvement of one or more family members may be required for genetic testing to be informative, and parents may feel guilt about passing inherited risk on to their children.

Knowledge about a cancer-predisposing mutation can be informative not only for the individual tested but also for other family members. Family members who previously had not considered the implications of their family history for their own health may be led to do so, and some will undergo genetic testing, resulting in more definitive information on whether they are at increased genetic risk. Some relatives may learn their mutation status without being directly tested, for example, when a biological parent of a child who is a known mutation carrier is identified as an obligate carrier. Founder effects may result in the recognition that specific ethnic groups have a higher prevalence of certain mutations, knowledge that can be both clinically useful (permitting more rational genetic testing strategies) or potentially stigmatizing. Testing may reveal the presence of nonpaternity in a family. There is the theoretical possibility that genetic information may be misused, and concerns about the potential for insurance and/or employment discrimination may arise. Genetic information may also affect medical and lifestyle decisions.

Refer to individual PDQ summaries for available evidence addressing all ancillary issues.


1. Lindor NM, Lindor CJ, Greene MH: Hereditary neoplastic syndromes. In: Schottenfeld D, Fraumeni JF Jr, eds.: Cancer Epidemiology and Prevention. 3rd ed. New York, NY: Oxford University Press, 2006, pp 562-76.


Genetic counseling is a process of communication between genetics professionals and patients with the goal of providing individuals and families with information on the relevant aspects of their genetic health, available testing and management options, and support as they move toward understanding and incorporating this information into their daily lives. Genetic counseling generally involves six steps:

  1. Family and medical history assessment.
  2. Analysis of genetic information.
  3. Communication of genetic information.
  4. Education about inheritance, genetic testing, management, risk reduction, resources and research opportunities.
  5. Supportive counseling to facilitate informed choices and adaptation to the risk or condition.
  6. Follow up. [1]

Genetic evaluation involves an interaction with a medical geneticist or other genetics professional and may include a physical examination and diagnostic testing, in addition to genetic counseling. The principles of voluntary and informed decision making, nondirective and noncoercive counseling, and protection of client confidentiality and privacy are central to the philosophy of genetic counseling. [1] [2] [3] [4] [5] Refer to the PDQ summary on Elements of Cancer Genetics Risk Assessment and Counseling for more information on the nature and history of genetic counseling.

From the mid 1990s to the mid 2000s, genetic counseling expanded to include discussion of genetic testing for cancer risk, as more genes associated with inherited cancer risk were discovered. Cancer genetic counseling often involves a multidisciplinary team of health professionals that may include a genetic counselor, an advanced practice genetics nurse, or a medical geneticist; a mental health professional; and various medical experts such as an oncologist, surgeon, or internist. The process of counseling may require a number of visits to address medical, genetic testing, and psychosocial issues. Even when cancer risk counseling is initiated by an individual, inherited cancer risk has implications for the entire family. Because genetic risk affects biological relatives, contact with these relatives is often essential to collect accurate family and medical histories. Cancer genetic counseling may involve several family members, some of whom will have had cancer and others who have not.

The impact of risk assessment and predisposition genetic testing is improved health outcomes. The information derived from risk assessment and/or genetic testing allows the health care provider to tailor an individual approach to health promotion and optimize long-term health outcomes through the identification of at-risk individuals before cancer develops. The health care provider can thus intervene earlier either to reduce the risk or diagnose a cancer at an earlier stage, when the chances for effective treatment are greatest. The information may be used to modify the management approach to an initial cancer, clarify the risks of other cancers, or predict the response of an existing cancer to specific forms of treatment, all of which may alter treatment recommendations and long-term follow-up.


1. Resta R, Biesecker BB, Bennett RL, et al.: A new definition of Genetic Counseling: National Society of Genetic Counselors' Task Force report. J Genet Couns 15 (2): 77-83, 2006.

2. Baker DL, Schuette JL, Uhlmann WR, eds.: A Guide to Genetic Counseling. New York, NY: Wiley-Liss, 1998.

3. Bartels DM, LeRoy BS, Caplan AL, eds.: Prescribing Our Future: Ethical Challenges in Genetic Counseling. New York, NY: Aldine de Gruyter, 1993.

4. Kenen RH: Genetic counseling: the development of a new interdisciplinary occupational field. Soc Sci Med 18 (7): 541-9, 1984.

5. Kenen RH, Smith AC: Genetic counseling for the next 25 years: models for the future. J Genet Couns 4(2): 115-124, 1995.

Structure and Content of PDQ Summaries

PDQ cancer genetics summaries focus on the genetics of specific cancers, inherited cancer syndromes, and the ethical, social, and psychological implications of cancer genetics knowledge. Sections on the genetics of specific cancers include syndrome-specific information on the risk implications of a family history of cancer, the prevalence and characteristics of cancer-predisposing mutations, known modifiers of genetic risk, opportunities for genetic testing, outcomes of genetic counseling and testing, and interventions available for people with increased cancer risk resulting from an inherited predisposition.

The source of medical literature cited in PDQ cancer genetics summaries is peer-reviewed scientific publications, the quality and reliability of which is evaluated in terms of levels of evidence. Where relevant, the level of evidence is cited, or particular strengths of a study or limitations of the evidence are described.

Creating evidence-based summaries on cancer genetics is challenging because the rapid evolution of new information often results in evidence that is incomplete or of limited quality. In addition, established methods for evaluating the quality of the evidence are available for some but not all aspects of cancer genetics. Varying levels of evidence are available for different topics, and PDQ summaries are subject to modification as new evidence becomes available. As in other areas of medicine, testing and treatment decisions must be based on information that sometimes falls short of the optimal level of evidence. Recognizing the limits inherent in certain observations will alter the weight given to recommendations based on that evidence and serves to keep our minds open to new improved information, as it comes along.

The quality of evidence depends on the appropriateness of the study to the question being evaluated and on how well the study was designed, implemented, analyzed, and interpreted. For evaluating outcomes of both medical and social interventions, the strongest evidence is obtained from well-designed and well-conducted randomized clinical trials. For evaluating other questions, particularly those related to the prevalence of gene variants and inherited syndromes and determining the clinical validity of genetic tests, the strongest evidence is obtained from well-designed descriptive studies. Particular elements of study design, such as the nature of the population studied or the duration of observation, may be crucial to assessing the quality of a study.

During the early phases of research in a new area, information relevant to the needs of patients and clinicians may come from work at all levels of evidence, including well-designed quasi-experimental studies (nonrandomized, controlled single-group, pre/post, cohort, time, or matched case-control series) or nonexperimental studies (case reports, clinical examples, qualitative or narrative studies, or theoretical work). Such research may yield information important to patients and clinicians, who must make management decisions before full data on the risks and benefits of cancer genetic testing are available. In addition, such work helps to inform future research using more rigorous designs.

Study Populations

The level of evidence required for informed decision making about genetic testing depends on the circumstances of testing. Evidence from a sample of high-risk families may be sufficient to provide useful information for testing decisions among people with similar family histories but is likely to be insufficient to make early recommendations for, or decisions about, testing in families with less dramatic histories or in the general population. Even among people with similar family histories, however, other contributing genes or different exposures could modify the effect of a gene mutation in different families. In evaluating evidence, the most important consideration is the relevance of the available data to the patient for whom a genetic assessment is being considered. In summaries addressing the cancer risk associated with genetic polymorphisms and mutations, the study populations used for each risk assessment will be noted, according to the following categories.

  1. Population-based.
  2. Proxy for population-based. (The study population selected is assumed to be generally representative of the population from which it is drawn. For example: Persons participating in a community-based Tay-Sachs screening program, as a proxy for persons of Jewish descent.)
  3. Public recruitment of volunteers, e.g., using a newspaper ad.
  4. Sequential case series.
  5. Convenience sample.
  6. An affected family or several families.

Use of Levels of Evidence

The PDQ editorial boards use a ranking system of levels of evidence to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. For any given therapy, results of prevention and treatment studies can be ranked on each of the following two scales: (1) strength of the study design and (2) strength of the endpoints. Together, the two rankings provide a measure of the overall level of evidence. Screening studies are ranked on strength of study design alone. Depending on perspective, different expert panels, professional organizations, or individual physicians may use different cut-off points related to overall strength of evidence in formulating therapeutic guidelines or in taking action; however, a formal description of the level of evidence provides a uniform framework for the data, leading to specific recommendations.

There are varying levels of evidence related to screening, prevention, and treatment that support a given summary. The summaries are subject to modification as new evidence becomes available. The strongest evidence would be that obtained from a well-designed and well-conducted randomized controlled trial. It is not always practical, however to conduct such a trial to address every question in the fields of cancer screening, prevention, and treatment.

Evidence related to screening

The PDQ Cancer Genetics Editorial Board has adopted the following definitions related to screening:

Five requirements should be met before it is considered appropriate to screen for a particular medical condition as part of routine medical practice: [1] [2]

  1. The medical condition being sought must cause a substantial burden of suffering, measured both as mortality and as the frequency and severity of morbidity and loss of function.
  2. A screening test or procedure exists that will detect cancers earlier in their natural history than when diagnosis is prompted by symptoms, and this test must be acceptable to patients and society in terms of convenience, comfort, risk, and cost.
  3. Strong evidence exists that early detection and treatment improve disease outcomes, particularly disease-specific survival.
  4. The harms of screening must be known and acceptable.
  5. Screening must be judged to do more good than harm, considering all benefits and harms it induces, as well as the cost and cost-effectiveness of the screening program.

In order of strength of evidence, the levels for screening studies follow:

  1. Evidence obtained from at least one well-designed and well-conducted randomized controlled trial.
  2. Evidence obtained from well-designed and well-conducted nonrandomized controlled trials.
  3. Evidence obtained from well-designed and well-conducted cohort or case-control analytic studies, preferably from more than one center or research group.
  4. Evidence obtained from multiple time series, with or without intervention.
  5. Opinions of respected authorities based on clinical experience, descriptive studies, or reports of expert committees.

Evidence related to cancer prevention

Prevention is defined as a reduction in the incidence (or the rate) of new cancer, with the goal of reducing cancer-related morbidity and mortality. Examples of prevention strategies include smoking cessation, avoidance of excessive exposure to sunlight (ultraviolet) or ionizing radiation, surgical removal of an at-risk target organ before cancer develops, and use of medications (e.g., tamoxifen for breast cancer risk reduction).

For each prevention-related summary of evidence statement, the associated levels of evidence are listed. In order of strength of evidence, the five levels are as follows:

  1. Evidence obtained from at least one well-designed and well-conducted randomized controlled trial that has:
    1. A cancer endpoint.
      1. Mortality
      2. Incidence
    2. A generally accepted intermediate endpoint (e.g., large adenomatous polyps for studies of colorectal cancer prevention).
  2. Evidence obtained from well-designed and well-conducted nonrandomized controlled trials that have:
    1. A cancer endpoint.
      1. Mortality
      2. Incidence
    2. A generally accepted intermediate endpoint (e.g., large adenomatous polyps for studies of colorectal cancer prevention).
  3. Evidence obtained from well-designed and well-conducted cohort or case-control studies, preferably from more than one center or research group, that have:
    1. A cancer endpoint.
      1. Mortality
      2. Incidence
    2. A generally accepted intermediate endpoint (e.g., large adenomatous polyps for studies of colorectal cancer prevention).
  4. Ecologic (descriptive) studies (e.g., international patterns studies, migration studies) that have:
    1. A cancer endpoint.
      1. Mortality
      2. Incidence
    2. A generally accepted intermediate endpoint (e.g., large adenomatous polyps for studies of colorectal cancer prevention).
  5. Opinions of respected authorities based on clinical experience or reports of expert committees (e.g., any of the above study designs using invalidated surrogate endpoints).

In assessing a genetic test (or other method of genetic assessment, including family history), the analytic validity, clinical validity, and clinical utility of the test need to be considered. [3]

Evidence related to treatment

For each treatment-related summary of evidence statement, the associated levels of evidence are listed. In order of strength of evidence, the five levels are as follows:

  1. Evidence obtained from randomized controlled trials.
  2. Evidence obtained from nonrandomized controlled trials.
  3. Evidence obtained from cohort or case-control studies.
    1. Total mortality (or overall survival from a defined time).
    2. Cause-specific mortality (or cause-specific mortality from a defined time).
    3. Carefully assessed quality of life.
    4. Indirect surrogates.
      1. Disease-free survival.
      2. Progression-free survival.
      3. Tumor response rate.
  4. Evidence from ecological, natural history, or descriptive studies.
  5. Opinions of respected authorities based on clinical experience, descriptive studies, or reports of expert committees.

Analytic Validity

Analytic validity refers to how well the genetic assessment performs in measuring the property or characteristic it is intended to measure. In the case of family history, analytic validity refers to the accuracy of the reported family history information. In the case of a test for a specific mutation, analytic validity refers to the accuracy of a genetic test in identifying the presence or absence of the mutation. The analytic validity of a genetic test is affected by the technical accuracy and reliability of the testing procedure and by the quality of the laboratory processes (including specimen handling).

The assessment of analytic validity is complex for some genetic tests. For example, a panel test is designed to evaluate a particular set of mutations (e.g., the Ashkenazi founder mutations in the BRCA1 and BRCA2 genes), and the analytic validity of the different components of the test may vary. Some genetic tests involve evaluating the DNA sequence of portions of a gene to determine whether any mutations are present (including mutations not previously identified). The sensitivity and specificity of these sequencing tests may vary with the laboratory techniques employed, the proportion of the gene tested, and the structural nature of the mutations present in the gene.

Clinical Validity

Clinical validity refers to the predictive value of a test for a given clinical outcome (e.g., the likelihood that cancer will develop in someone with a positive test) and is primarily determined by the sensitivity and specificity with which a test identifies people with a defined clinical condition within a given population. Sensitivity of a test refers to the proportion of persons who test positive among all those who actually have a clinical condition; specificity refers to the proportion of persons who test negative from among all those who do not have the clinical condition. In the case of genetic susceptibility to cancer, clinical validity can be considered at two levels:

  1. Does a positive test identify a person as having an increased risk of cancer?
  2. If so, how high is the cancer risk associated with a positive test?

Thus, the clinical validity of a genetic test is the likelihood that cancer will develop in someone with a positive test result. This likelihood is affected not only by the presence of the gene mutation itself but also by any other modifying factors that might affect the penetrance of the mutation (e.g., the mutation carrier's environmental exposures or personal behaviors) or by the presence or absence of mutations in other genes. For this reason, the clinical validity of a genetic test for a specific mutation may vary in different populations. If the cancer risk associated with a given mutation is unknown or variable, a test for the mutation will have uncertain clinical validity. A summary of definitions of concepts relevant to understanding clinical validity and other aspects of cancer genetics testing has been published. [4] The test should be evaluated in the population in which the test will be used.

Clues to whether a particular familial cancer syndrome has a genetic basis can be derived informally, by inspecting the pattern of affected persons and unaffected persons in a series of families; or more formally, using an analytic technique known as segregation analysis. Segregation analysis provides quantitative data in support of, or against, the likelihood that a particular genetic mode of inheritance might explain the patterns observed in the study families.

Evidence that a particular gene might explain a specific cancer predisposition syndrome often derives initially from linkage studies that use collections of families meeting stringent clinical criteria for a specific cancer susceptibility syndrome. The demonstration of strong linkage of cancer susceptibility to a gene or genetic region in a pattern consistent with autosomal dominant inheritance provides evidence in support of both the mode of inheritance and the particular gene that might underlie the risk. Once linkage is established, a strong case for association between the genetic trait and disease can be made, even though the families used in the study may not be representative of the general population. The genetic trait measured in linkage studies is not always the causal factor itself but may be a genetic trait closely linked to it. Additional molecular studies are required to identify the specific gene associated with inherited risk, after linkage studies have determined its general chromosomal location.

Linkage studies, however, provide only limited evidence concerning either the range of cancer types associated with a mutation or the magnitude of risk and lifetime probability of cancer conferred by a mutation in less selected populations. In addressing these questions, the best information for clinical decisions comes from naturally occurring populations in which people with all degrees of risk are represented, similar to those in which clinical or public health decisions must be made. Thus, observations about cancer risk in families having multiple members with early breast cancer are applicable only to other families meeting those same clinical criteria. Ideally, the families tested should also have similar exposures to factors that can modify the expression of the gene(s) being studied. The mutation-associated risk in other populations, such as families with less dramatic cancer aggregation, or in the general population can best be assessed by direct study of those populations.

Clinical Utility

The clinical utility of the test refers to the likelihood that the test will, by prompting an intervention, result in an improved health outcome. The clinical utility of a genetic test is based on the health benefits related to the interventions offered to persons with positive test results. Theoretically, there are at least five strategies that might improve the health outcome of people with a genetic susceptibility to cancer:

Evaluation of interventions should consider their efficacy (capacity to produce an improved health outcome) and effectiveness (likelihood that the improved outcome will occur, taking into account actual use of the intervention and recommended follow-up). Sometimes genetic information may lead to consideration of changes in the approach to clinical management, based on expert opinion, in the absence of proof of clinical utility.


1. Woolf SH: Screening for prostate cancer with prostate-specific antigen. An examination of the evidence. N Engl J Med 333 (21): 1401-5, 1995.

2. Winawer S, Fletcher R, Rex D, et al.: Colorectal cancer screening and surveillance: clinical guidelines and rationale-Update based on new evidence. Gastroenterology 124 (2): 544-60, 2003.

3. Holtzman NA, Watson MS, eds.: Promoting Safe and Effective Genetic Testing in the United States: Final Report of the Task Force on Genetic Testing. Baltimore, Md: Johns Hopkins Press, 1998. Also available online. Last accessed June 28, 2007.

4. Grann VR, Jacobson JS: Population screening for cancer-related germline gene mutations. Lancet Oncol 3 (6): 341-8, 2002.

Genetic Resources

Health care providers who deliver genetic services, including genetic counseling can be located through local, regional, and national professional genetics organizations; through the NCI Web site Cancer Genetics Services Directory; and through the Gene Tests-Gene Clinics Web site. Providers of cancer genetic services are not limited to one specialty and include medical geneticists, genetic counselors, advanced practice genetics nurses, oncologists (medical, radiation, or surgical), other surgeons, internists, family practitioners, and mental health professionals. A cancer genetics health care provider will assist in constructing and evaluating a pedigree, eliciting and evaluating personal and family medical histories, and calculating and providing information about cancer risk and/or probability of a mutation being associated with cancer in the family. In addition, if a genetic test is available, these providers can assist in pretest counseling, laboratory selection, informed consent, test interpretation, posttest counseling, and follow-up. Please see the Table of Links at the end of this summary in printable view for the Genetic Resources URLs.

Clinical Genetics

Resource Description
GeneTests Information for health professionals about hundreds of genetic tests and the laboratories performing those tests.
Human Genome Epidemiology Network (HuGENet) Network for sharing population-based human genome epidemiologic information.
INFOGENETICS Clinical practice tools.
Online Mendelian Inheritance in Man (OMIM) Catalog of human genes and genetic disorders.

Consumer/Client: General Information

Resource Description
The DNA Files Series of 14 1-hour public radio documentaries and related information.
Dolan DNA Learning Center Gene Almanac Variety of educational resources, including an interactive DNA timeline.
FORCE: Facing Our Risk of Cancer Empowered Provides support and information to individuals and families affected by hereditary breast and ovarian cancer through a toll-free help line, message boards, chat, and support groups.
Genetics Education Center Material for educators.
Genetics Home Reference—National Library of Medicine Consumer information about genetic conditions and the genes or chromosomes responsible for those conditions.
Genetic and Rare Diseases Information Center Information service for the general public, including patients and their families as well as health care professionals and biomedical researchers.
Genetic Science Learning Center Basic genetics, genetic disorders, genetics in society, and several thematic units.
The Human Genome Project: Exploring Our Molecular Selves Downloadable modules or online viewing of The Human Genome Project, including milestones, a talking glossary, classroom activities, and a 3-D computer-animated video on basic molecular biology.
The National Cancer Institute’s Dictionary of Genetics Terms Contains definitions for more than 100 terms related to genetics.
The New Genetics: A Resource for Students and Teachers Links to genetics education resources.
Understanding Cancer Series: Gene Testing (from the National Cancer Institute) Primer on genetic testing.

Ethical, Legal and Social Implications (ELSI), Policy, and Legislation

Resource Description Links to articles on genetics and bioethics.
Bioethics Resources on the Web Links to bioethics resources.
Council for Responsible Genetics Information on the social, ethical, and environmental implications of genetic technologies.
DNA Patent Database Searchable database of U.S. DNA-based patents and patent applications issued by the U.S. Patent and Patent Applications Trademark Office.
Ethical, Legal, and Social Issues (from the Human Genome Project) Information, articles, and links on a wide range of issues. Information on the social, ethical, and policy issues associated with genetic and genomic knowledge and technology.
Genetics and the Law (from the Council for Responsible Genetics) Searchable online clearinghouse of information on emerging legal developments in human genetics.
Genetics and Public Policy Center Information on public policy related to human genetic technologies for the public, media, and policy makers.
Genome Technology and Reproduction: Values and Public Policy and Communities of Color and Genetics Policy Project Two subprojects combined to form a 5-year project designed to provide policy recommendations based on public perceptions and responses to the explosion of genetic information and technology.
HumGen International Comprehensive international database on the legal, social, and ethical aspects of human genetics.
NCSL (National Conference of State Legislatures) Genetic Technologies Project Resources on a variety of genetics public policy and related issues for state legislators, legislative staff, and other policy makers.
National Information Resource on Ethics and Human Genetics Links to resources and databases on ethics and human genetics.
National Information Resource on Ethics and Human Genetics: Annotated Bibliographies: Scope Note Series Annotated bibliographies on various genetics and ethics issues.
National Human Genome Research Institute (NHGRI) Policy and Legislation Database Searchable database of Federal and State laws/ statutes, Federal legislative materials, and Federal administrative and executive materials about privacy of genetic information/ confidentiality; informed consent; insurance and employment discrimination; genetic testing and counseling; and commercialization and patenting.
National Society of Genetic Counselors (NSGC) Code of Ethics A statement to clarify and guide the ethical conduct of genetic counselors.
The President's Council on Bioethics Reports, transcripts, and background material on current bioethical issues.
THOMAS Legislative Information (from Library of Congress) Searchable database of U.S. legislation (current and previous Congresses).
Your Genes, Your Choices Description of the Human Genome Project, the science behind it, and the ethical, legal, and social issues raised by the project.

Family History Tools

Resource Description
American Medical Association: Family History Tools Tools for gathering family history and links to resources.
Family History: Resources and Tools CDC’s Web site devoted to using family history to promote health.
National Society of Genetic Counselors: Your Family History—Your Future Information on collecting a family health history.
U.S. Surgeon General’s Family History Initiative: My Family Health Portrait Web-based family history tool, created by the office of the U.S. Surgeon General.

Genome Research

Resource Description
BLAST Search (part of the Ensembl Project; see below) Search protein or DNA sequence against metazoan genomes.
The Cancer Genome Anatomy Project (CGAP) Access to all CGAP data and biological resources.
CancerGenes Combines gene lists annotated by experts with information from key public databases such as Entrez Gene, COSMIC, and iHOP.
Cancer Genome Workbench (CGWB) Integrates clinical tumor mutation profiles with the reference human genome to improve the accuracy of mutation identification.
Chromosomal Variation in Man Searchable database of literature citations on chromosomal variants and anomalies.
Ensembl (Joint software project between the European Bioinformatics Institute and the Wellcome Trust Sanger Institute) Data sets resulting from an automated genome analysis and annotation process.
Genome Channel Java viewers for human genome data.
Genome Sequencing Center: Homo sapiens Maps Links to clone and accession maps of the human genome.
KMcancerDB Human gene mutation database with graphical display of molecular information for cancer-related genes.
National Center for Biotechnology Information: Genomic Biology Views of chromosomes, maps, and loci; links to other NCBI resources.
Online Mendelian Inheritance in Man (OMIM) Catalog of human genes and genetic disorders.
International HapMap Project A variety of ways to query for SNPs in the human genome.
UCSC Genome Bioinformatics Reference sequence for the human and C. elegans genomes and working drafts for the mouse, rat, Fugu, Drosophila, C. briggsae, yeast, and SARS genomes.

Health Professional Practice and Education

Resource Description
Centre for Education in Medical Genetics Develops, provides, and evaluates genetics education opportunities and resources.
Centre for Genetics Education Education and service resources for patients and professionals.
Dolan DNA Learning Center Gene Almanac Interactive multimedia genetics education resources.
Essential Nursing Competencies and Curricula Guidelines for Genetics and Genomics Establishes minimum basis to prepare the nursing workforce to deliver competent genetic and genomic-focused nursing care. Created by consensus panel in 2005.
GenEd Project Information about the project, news, and links to previously published research on European aspects of genetic services.
Genetics in Clinical Practice: A Team Approach Interactive virtual genetics clinic with case scenarios and case discussions. Target audience is primary care professionals.
Genetics Education Center For educators interested in human genetics and the Human Genome Project.
Genetics Education Program for Nurses (GEPN) Sample genetics nursing course syllabi and other genetics educational opportunities and resources for nurses.
Genetics in Primary Care Training program curriculum materials.
Genetics in Psychology American Psychological Association's genetics site.
Genetics and Your Practice Online modules for health care professionals designed for exploration of a topic rather than a sequential presentation of material. Includes fact sheets and sample clinical forms. Free registration required for access.
Medical School Core Curriculum in Genetics Medical school course competencies, skills, knowledge, and behaviors that should be covered in a genetics curriculum developed by the Association of Professors of Human and Medical Genetics and the American Society of Human Genetics.
National Coalition for Health Professional Education in Genetics (NCHPEG) Core competencies in genetics and reviews of education programs. Descriptions of available instructional resources, courses, and institutes.
Six Weeks to Genomic Awareness Webcast of six lessons in genomics for public health professionals.

Institutional Review Boards (IRBs)

Resource Description
Genetic Testing and Screening in the Age of Genomic Medicine. New York State Task Force on Life and the Law. Includes general and state-specific information in a bulleted report.
Pharmacogenetics: Ethical Issues. Nuffield Council on Bioethics. Includes a section discussing the use of pharmacogenetics in clinical trials.
Protecting Human Research Subjects Institutional Review Board Guidebook, Chapter V, Section H: Human Genetic Research. Office for Human Research Protections. Discusses many issues that continue to challenge IRBs investigators, and policy makers today.

Professional Organizations: Genetics

Resource Description
American Board of Genetic Counseling (ABGC) Information about certification of genetic counselors.
American Board of Medical Genetics (ABMG) Information about medical genetic training programs and certification of geneticists.
American College of Medical Genetics (ACMG) Resources, policy statements, and practice guidelines about medical genetics.
American Society for Human Genetics (ASHG) Resources, projects, and policies concerning human genetics.
Genetics Nursing Credentialing Commission (GNCC) Information about credentialing of genetics nurses.
Genetics Society of America (GSA) Links to teaching Web sites, general educational courses, and journals and publications about genetics.
International Society of Nurses in Genetics (ISONG) Resources to help nurses incorporate new knowledge about human genetics into practice, education, and research.
National Society of Genetic Counselors (NSGC) Information about genetic counseling: practice guidelines, links to genetic counselors, and genetic discrimination resources.

Risk Assessment

Resource Description
Harvard Center for Cancer Prevention: Your Disease Risk Personalized estimation of cancer risk and tips for prevention.
JamesLink: Personalized Cancer Risk Assessment Interactive tool that estimates cancer risk by reviewing patterns of cancer in a family.
My Generations Interactive tool that estimates cancer risk by reviewing patterns of cancer in a family.
National Cancer Institute: Breast Cancer Risk Assessment Tool Interactive tool for estimating a woman's risk of developing invasive breast cancer.
National Cancer Institute: Melanoma Risk Assessment Tool Interactive tool for estimating an individual’s absolute risk of developing melanoma.

Online Gene Mutation Prediction Programs

Resource Description
HuGE Risk Translator Calculates the predictive value of genetic markers.
MRC Human Genetics Unit, Edinburgh Predicts the likelihood of mutations in one of the mismatch repair genes in persons with colon cancer.
The Penn II Risk Model Estimates the probability that an individual has a BRCA1 or BRCA2 mutation.
PREMM1,2 Model: Prediction Model for MLH1 and MSH2 Gene Mutations Estimates the probability that an individual carries a mutation in one of the mismatch repair genes.

Search Engines Specializing in Genetics and Genomics

Resource Description
Genetics Resources on the Web (GROW) Information related to human genetics, with a particular focus on genetic medicine and health.
Georgetown University: National Information Resource on Ethics and Human Genetics Search engine for literature on specific issues related to ethics and human genetics.
HuGE Navigator An integrated, searchable knowledge base of genetic associations and human genome epidemiology.

United States Government Agencies

Resource Description
Centers for Disease Control and Prevention: National Office of Public Health Genomics Information on how human genomic discoveries can be used to improve health and prevent disease, including links to many resources.
Department of Energy Office of Science: Genomics educational resources.
Department of Health and Human Services Links to publications and materials available for purchase or download from the HRSA Information Center.
Genetic Modification Clinical Research Information System (GeMCRIS) Information about human gene transfer trials registered with NIH.
National Cancer Institute NCI’s summaries of cancer genetics–related information.
National Human Genome Research Institute Research, policy, ethics, education, and training information and resources about genetic and rare diseases.
National Institute of Environmental Health Sciences (NIEHS): Environmental Genome Project Information on project to improve understanding of human genetic susceptibility to environmental exposures.

Get More Information From NCI

Call 1-800-4-CANCER

For more information, U.S. residents may call the National Cancer Institute's (NCI's) Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 9:00 a.m. to 4:30 p.m. Deaf and hard-of-hearing callers with TTY equipment may call 1-800-332-8615. The call is free and a trained Cancer Information Specialist is available to answer your questions.

Chat online

The NCI's LiveHelp online chat service provides Internet users with the ability to chat online with an Information Specialist. The service is available from 9:00 a.m. to 11:00 p.m. Eastern time, Monday through Friday. Information Specialists can help Internet users find information on NCI Web sites and answer questions about cancer.

Write to us

For more information from the NCI, please write to this address:

Search the NCI Web site

The NCI Web site provides online access to information on cancer, clinical trials, and other Web sites and organizations that offer support and resources for cancer patients and their families. For a quick search, use our “Best Bets” search box in the upper right hand corner of each Web page. The results that are most closely related to your search term will be listed as Best Bets at the top of the list of search results.

There are also many other places to get materials and information about cancer treatment and services. Hospitals in your area may have information about local and regional agencies that have information on finances, getting to and from treatment, receiving care at home, and dealing with problems related to cancer treatment.

Find Publications

The NCI has booklets and other materials for patients, health professionals, and the public. These publications discuss types of cancer, methods of cancer treatment, coping with cancer, and clinical trials. Some publications provide information on tests for cancer, cancer causes and prevention, cancer statistics, and NCI research activities. NCI materials on these and other topics may be ordered online or printed directly from the NCI Publications Locator. These materials can also be ordered by telephone from the Cancer Information Service toll-free at 1-800-4-CANCER (1-800-422-6237), TTY at 1-800-332-8615.

Changes to This Summary (06/17/2008)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Genetics Resources

Added text about the National Human Genome Research Institute Policy and Legislation Database as an Ethical, Legal and Social Implications, Policy, and Legislation resource.

Added text about the National Society of Genetic Counselors (NSGC) Code of Ethics as an Ethical, Legal and Social Implications, Policy, and Legislation resource.

More Information

About PDQ

Additional PDQ Summaries


This information is intended mainly for use by doctors and other health care professionals. If you have questions about this topic, you can ask your doctor, or call the Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).

Date first published 2006-11-13

Date last modified 2008-02-28