6.1 Unit Overview
Learning Objectives
- Explain the importance and the process of taking a detailed three-generation family health history.
- Identify and use the symbols found in pedigree charts.
- Analyze pedigree charts to determine the genotypes and phenotypes of individuals in the chart and the probabilities of inheritance.
- Identify the patterns of inheritance of autosomal dominant and recessive, x-linked dominant and recessive, and y-linked traits in humans.
- Recognize the numerous interacting factors that contribute to polygenic risk.
Outline
Topics covered in this chapter include:
- Family history
- Constructing a pedigree chart
- Pedigree analysis and modes of inheritance
- Calculating probabilities using pedigree charts
- Polygenic risk scores
Competencies Nurses will Develop in this Chapter
ANA (2023):
Nursing assessment: Applying/integrating genomic knowledge:
- Collects, reviews, and updates personal and family health history to include any genomic testing and environmental and other risk factors.
- Conducts health and physical assessments that incorporate knowledge about known or potential environmental, genomic, and other risk factors (e.g., behavioral, lifestyle).
- Assesses clients’ knowledge, perceptions, and responses to genomic information about themselves and their family members.
Identification:
- Evaluates assessment data to identify clients who may benefit from specific genomic information and services.
- Recognizes issues that undermine the rights of all clients for autonomous, informed genomic-related decision-making and voluntary action.
Referral activities:
- Facilitates referrals for specialized genomic services for clients as needed.
Provision of education, care, and support:
- Develops a plan of care in collaboration with the interdisciplinary team that incorporates genomic assessment information.
- Advocates for autonomous, informed genomic-related decision-making.
- Demonstrates in practice the importance of tailoring genomic information and services that are responsive to the unique attributes of every person.
- Uses health promotion and disease prevention practices that consider genomic influences as well as personal and environmental risk factors.
- Provides genomic health care in collaboration with interdisciplinary professionals and when possible clients and their families.
NHS (2023):
Identify individuals who might benefit from genomic services and/or information as part of assessing needs and planning care:
- recognizing the key indicators of a potential genetic condition, or clinical situation where genomics-informed healthcare would be appropriate; and
- recognizing the importance of family history in assessing predisposition to a genetic condition.
Advocate for the rights of all individuals to make informed decisions and act voluntarily:
- promoting and supporting equitable access to genomic services.
Demonstrate a knowledge and understanding of genomics in human development, variation and health to underpin effective practice:
- relating it to the maintenance of health and manifestation of conditions;
- relating it to the prevention and management of a genomic condition or response to treatment; and
- underpinned by core genomic concepts that form a sufficient knowledge base for understanding the implications of different conditions and clinical situations that may be encountered.
Obtain and communicate reliable, current information about genomics, for self, patients, families and colleagues:
- using information technologies and other information sources effectively to do so;
- applying critical appraisal skills to assess the quality of information accessed; and
- ensuring the information is appropriate for the intended audience.
Provide ongoing nursing care and support to patients, carers, families and communities with genomic healthcare needs:
- being responsive to changing needs through the life-stages and during periods of uncertainty.
Key terminology
Absolute risk
The likelihood of a disease occurring which remains true without any comparison to any groups of people (NHGRI, 2020, para. 10).
Affected
An individual that is known to have symptoms of the disease (Singh, 2023a, para. 4).
Carrier
A carrier, as related to genetics, is an individual who “carries” and can pass on to its offspring a genomic variant (allele) associated with a disease (or trait) that is inherited in an autosomal recessive or sex-linked manner, and who does not show symptoms of that disease (or features of that trait). The carrier has inherited the variant allele from one parent and a normal allele from the other parent. Any offspring of carriers is at risk of inheriting a variant allele from their parents, which would result in that child having the disease (or trait).
Consanguinity
Generally defined as a union between two individuals related as second cousins or closer (GECKO, n.d., para. 7).
Consultand
A person receiving genetic counseling (Singh, 2023a).
Pedigree chart
A pedigree, as related to genetics, is a chart that diagrams the inheritance of a trait or health condition through generations of a family. The pedigree particularly shows the relationships among family members and, when the information is available, indicates which individuals have a trait(s) of interest.
Polygenic risk score
A polygenic risk score (abbreviated PRS) uses genomic information alone to assess a person’s chances of having or developing a particular medical condition. A person’s PRS is a statistical calculation based on the presence or absence of multiple genomic variants, without taking environmental or other factors into account.
Proband
A proband is an individual who is affected by a genetic condition or who is concerned they are at risk. Usually, the proband is the first person in a family who brings the concern of a genetic disorder to the attention of healthcare professionals (Singh, 2023b).
Relative risk
A polygenic risk score tells you how a person’s risk compares to others with a different genetic constitution.
Risk, as related to genetics, refers to the probability that an individual will be affected by a particular heritable or genetic disorder. Both a person’s genome and environmental exposures can influence risk. An individual’s risk may be higher because they inherit a genetic variant (or allele) in one gene or a combination of many variants in different genes that increases susceptibility to or overtly causes a disorder. Other individuals may be at higher risk because they have been exposed to one or more environmental factors that promote the development of a certain disorder (NHGRI, 2020)
Sporadic
A disease not caused by a mutation inherited from a parent (Singh, 2023a).
Attribution & References
ANA (2023) Nursing Competencies are © American Nurses Association. Reprinted with permission. All rights reserved. Seek permission before reusing this portion of the page.
Except where otherwise noted, this page is adapted from:
- Talking Glossary of Genomic and Genetic Terms, Courtesy of: National Human Genome Research institute (NGHRI), Public Domain with attribution.
References
American Nurses Association (ANA). (2023). Essentials of genomic nursing: Competencies and outcome indicators (3rd ed.). https://www.nursingworld.org/nurses-books/ana-books/ebook-essentials-of-genomic-nursing-competencies-/
Genetics Education Canada: Knowledge Organization (GECKO). (n.d.). Family history red flags (general). https://www.geneticseducation.ca/resources-for-clinicians/family-history/point-of-care-tool-12
National Health Service (NHS). (2023). The 2023 genomic competency framework for UK nurses. https://www.genomicseducation.hee.nhs.uk/wp-content/uploads/2023/12/2023-Genomic-Competency-Framework-for-UK-Nurses.pdf
National Human Genome Research Institute (NHGRI). (2020, August 11). Polygenic risk scores. https://www.genome.gov/Health/Genomics-and-Medicine/Polygenic-risk-scores
National Human Genome Research Institute (NHGRI). (n.d.). Talking glossary of genetic and genomic terms. www.genome.gov
Singh, N. R. (2023a, February 1). 4.2 Symbols used in Pedigree Charts. In Introduction to Genetics. Pressbooks. https://opengenetics.pressbooks.tru.ca/chapter/sporadic-and-non-heritable-diseases/
Singh, N. R. (2023b, February 1). 4.4 Sporadic and Non-Heritable Diseases. In Introduction to Genetics. Pressbooks. https://opengenetics.pressbooks.tru.ca/chapter/sporadic-and-non-heritable-diseases/
