Learning Objectives
By the end of this section, you will be able to:
- Differentiate between genetics and genomics
- Identify common chromosomal and genetic conditions
- Consider the nurse’s role in the field of genetics
- Discuss the genomic framework’s impact on patient care
Many of the leading causes of death in the United States, such as cardiac diseases, cancers, and cerebrovascular disease, include genetic or genomic factors (Khoury, 2024). In fact, nearly all health conditions have some genetic or genomic factors that will affect health throughout the life span.
Increasing recognition of the significance of such factors has implications for health care professionals (HCPs) at all levels. Nurses, who compose the largest group among health care HCPs and who interact with patients at multiple levels, are in a unique position to integrate genetic and genomic concepts into clinical practice areas, including screening and prevention, diagnostics, therapeutic interventions, and evaluation of outcomes. The clinical application of genetic and genomic knowledge has major implications for the entire nursing profession regardless of academic preparation, role, or practice setting.
What Is Genetics?
The field of genetics refers to the study of heredity, focused on patterns of inheritance of specific characteristics or traits, including variations of a trait within a population. Composed of deoxyribonucleic acid (DNA) sequences located in an individual’s chromosomes, a gene is the basic functional unit of heredity found in the nucleus of every cell (Figure 30.2). DNA carries the genetic instructions that determine the development of physical and biologic characteristics. Ribonucleic acid (RNA), a nucleic acid present in all living cells, acts as a messenger carrying instructions from the DNA for controlling the synthesis of proteins. These instructions are coded in four amino acid chemical bases; adenine (A), guanine (G), cytosine (C), and thymine (T), which form a double-stranded helix held together by the hydrogen bonds of the base pairs of A paired with T, and C paired with G (Montgomery, 2021).
The primary focus of genetics DNA research involves the structure and function of single genes as well as possible variations of a gene and its distribution among a population.
Link to Learning
Click here to watch a video further explaining the structure and components of DNA molecules.
Genomics
The study of genes and how they interact with each other and the environment is called genomics (National Human Genome Research Institute [NHGRI], 2018). It includes the study of complex diseases such as heart disease, chronic obstructive pulmonary disease (COPD), diabetes, and cancer, disorders typically related more to a combination of environmental and genetic factors than to individual genes. A genomic approach to health care uses knowledge about genetic variation and environmental effects to augment the planning and provision of health care to individuals, families, and the community. This approach reveals opportunities for new diagnostic methods as well as new possible treatment modalities. Let’s look at an example of how planning is augmented in a case of familial hypercholesterolemia (FH).
- Background: Familial hypercholesterolemia (FH) is a genetic condition characterized by high cholesterol levels, specifically low-density lipoprotein (LDL) cholesterol, which increases the risk of cardiovascular disease. Early detection and management are crucial to prevent severe health outcomes.
- Genomic approach in planning and provision of care:
Risk assessment:- Genetic testing: Genetic testing can identify mutations in genes such as low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin type 9 (PCSK9), which are known to cause FH. This testing allows for early identification of individuals who are at high risk, even before symptoms appear.
- Family history: Collecting a detailed family history helps to identify other family members who might be at risk. This information is crucial for planning screening and preventive measures for relatives.
- Tailored treatment: Based on genetic test results, a personalized treatment plan can be developed. For instance, individuals with certain genetic mutations may respond better to specific medications such as statins, PCSK9 inhibitors, or other lipid-lowering therapies.
- Lifestyle modifications: Understanding how genetic variations interact with lifestyle factors allows nurses to provide personalized advice on diet, exercise, and other lifestyle changes to manage cholesterol levels effectively.
- Family screening programs: Implementing family-based screening programs ensures that relatives of the affected individual are also tested and monitored. This proactive approach helps in early diagnosis and intervention, potentially reducing the overall burden of cardiovascular disease in the community.
- Educational initiatives: Nurses can lead educational sessions for families and communities to raise awareness about FH, its genetic basis, and the importance of early detection and management.
- Regular follow-ups: Establishing a schedule for regular follow-ups allows for continuous monitoring of cholesterol levels and adjustment of treatment plans as necessary. This ongoing care is tailored to the individual’s genetic profile and response to treatment.
Human Genomic Variation
Although there is a considerable amount of genetic variation among humans, any two people’s genomes are about 99.6 percent identical and about 0.4 percent different (NHGRI, 2023). These differences, or genomic variants, are what make individuals unique. External factors such as environment, diet, and lifestyle also contribute to uniqueness. Some genomic variations do not affect genome function, such as eye color, skin color, and height, whereas other variations can influence how a person responds to medications or influence development of certain conditions (NHGRI, 2023).
Genetic Conditions and Chromosomal Differences
A genetic condition is any condition caused by a single gene mutation. To take a quick step back, a mutation refers to a change in the DNA sequence of an organism’s genetic material and can occur spontaneously during DNA replication or as a result of exposure to environmental factors such as radiation, chemicals, or viruses. Mutations can affect a single nucleotide (point mutation), a small segment of DNA, or large sections of chromosomes. Mutations can have various effects on an organism, depending on where they occur in the genome and the specific nature of the mutation. Some mutations may be harmless or have no noticeable effect, whereas others can lead to alterations in protein structure or function, potentially causing genetic disorders, diseases, or changes in an organism’s traits.
Sickle cell disease is a genetic condition caused by production of an abnormal type of hemoglobin, called hemoglobin S, which delivers less oxygen to tissues and causes erythrocytes to assume a sickle (or crescent) shape, especially at low oxygen concentrations. These abnormally shaped cells can then become lodged in narrow capillaries because they are unable to fold in on themselves to squeeze through, blocking blood flow to tissues and causing a variety of serious problems including painful joints, delayed growth, and even blindness and cerebrovascular accidents (strokes).
A chromosome is a structure made of protein and a single molecule of DNA that carries genetic information in the form of genes. Sometimes a genetic disease is not caused by a mutation in a gene but by the presence of an incorrect structure or number of chromosomes. This is known as a chromosomal condition. For example, Down syndrome is caused by the presence of an extra copy of chromosome 21, a condition known as trisomy 21. The most common cause of trisomy 21 is chromosomal nondisjunction during meiosis, or simply an error in the distribution of chromosomes during meiosis. The frequency of nondisjunction events appears to increase with age, so the frequency of bearing a child with Down syndrome increases in females over the age of 36. The age of the male parent matters less because nondisjunction is much less likely to occur in a sperm than in an egg.
Whereas Down syndrome is caused by having three copies of a chromosome, Turner syndrome is caused by women having just one copy of the X chromosome. Women with Turner syndrome are sterile because their sexual organs do not mature.
Genomic Conditions
A disorder that is caused by the loss or gain of DNA material is called a genomic condition. Recall that genomics is the study of genes and how they react with each other and the environment. Complex diseases, such as asthma, diabetes mellitus, and heart disease, are characterized by a multifactorial etiology. This means that multiple genes, each with a small effect, interact with environmental and lifestyle factors to influence disease risk (NHGRI, 2018). In contrast, Mendelian diseases are typically caused by mutations in a single gene with a clear pattern of inheritance (dominant, recessive, etc.). For instance:
- Asthma involves genetic predispositions (e.g., variations in genes related to immune system function) interacting with environmental triggers such as allergens, pollution, and respiratory infections.
- Diabetes, particularly type 2, is influenced by genetic variants affecting insulin production and glucose metabolism, combined with factors such as diet, physical activity, and higher weight.
- Heart disease encompasses various genetic components related to cholesterol metabolism, blood pressure regulation, and inflammatory responses, alongside lifestyle factors such as diet, smoking, and exercise.
Nursing Practice and the Genomic Framework
With greater understanding of genetics and genomic science has come a revolutionary reframing of our understanding of human health and disease, recognizing genomics as a central component of health, illness, risk for disease, and response to treatment. As a result, all health care disciplines, including nursing, have developed initiatives to promote the application of genomic knowledge into clinical practice. Nurses are uniquely positioned to incorporate genomic knowledge across all aspects of the health care system, enhancing the provision of health care across the life span, addressing the needs of the individual patient, the family, and the community.
Essential competencies for nursing practice, regardless of role or level of preparation include
- integrating and applying genetic/genomic knowledge;
- demonstrating an understanding of genetics as related to screening, health promotion, and illness prevention;
- obtaining a comprehensive family history and developing a three-generation pedigree (visual representation of a family’s health history);
- analyzing findings to identify risk factors;
- identifying those who may benefit from genetic counseling services;
- making appropriate referrals for specialty care; and
- providing patient/family education and support.
Precision Health and Care
Precision health refers to the provision of personalized treatment based on individual needs. There can be a great deal of variability in the way different individuals respond to the same medication. Therapeutic response depends on a complex series of physiologic reactions; the medication is initially absorbed and distributed to the target tissue, where it is further metabolized, then finally excreted. Genetic variables have been found to account for 15 to 30 percent of the variability in drug response among different individuals. This percentage means that genetics explains a substantial portion of why people respond differently to the same drug. Luckily, genetic variables are not the sole factor (Anunobi, 2024).
Pharmacogenetics and Pharmacogenomics
Pharmacogenetics and pharmacogenomics are two very new terms in the realm of health care, which overall refer to an area of research examining how genes affect the response to medications. Although with similar meanings they may be seen used interchangeably, each has a specific distinguishing factor. The study of the variability of therapeutic responses to medications, as influenced by variations in single genes, is called pharmacogenetics. It examines factors such as specific drug receptors, and how drugs are metabolized and transported in the body, with the goal of developing individualized treatment based on the optimal choice of drug at the most effective dose.
The study of variations in multiple genes as associated with variable drug responses, rather than in single genes, is called pharmacogenomics. Pharmacogenomic studies investigate genetic variation among large population groups to ascertain differences in therapeutic responses for differing ethnic groups (NHGRI, 2018).