Genetic Issues for Perinatal Nurses, 3rd Edition Judith A. Lewis, PhD, RN, WHNP-BC, FAAN
The Human Genome Project • Began in 1990 as an international consortium, including the NIH and Department of Energy • Human genome sequencing announced in 2003, opening a new era in understanding health and illness • Continues to address ethical, legal and social implications • www.genome.gov
Relevance to Nursing • All nurses must be competent in genetics and genomics. • The Consensus Panel on Genetic/Genomic Nursing Competencies (2006) developed essential genetic/genomic nursing competencies and curricula guidelines. • Several nursing organizations have published practice guidelines related to genetics and genomics.
Terminology • Genetics— The study of individual genes, including the impact of individual genes on relatively rare disorders. • Genomics—The study of all genes in the human genome, including the study of interactions among genes and interactions between genes and the environment • (Guttmacher & Collins, 2002)
Terminology (Continued) • Genetic counseling—A communication process that deals with human problems associated with the occurrence, or the risk of occurrence, of a genetic disorder in a family(American Society of Human Genetics, 1975). • Genetic evaluation—Broader than genetic counseling; includes information gathering, information sharing and value-neutral counseling.
Terminology (Continued) • Informed consent—The process of communication between a client and a health care provider that results in the client’s authorization or agreement to undergo a specific medical intervention (American Medical Association, 2009).
Genetics Health Professionals • Medical geneticists—MD or PhD degree with advanced training in genetics • Physicians—Certification available from the American Board of Medical Genetics • Genetic counselors—Master’s degree; certification available from the American Board of Genetic Counseling
DNA Structure and Replication • DNA provides the codes for proteins. It is a double helix made of two strands held together with chemical bonds. • DNA replicates by undoing the bonds and creating a complementary strand. • As the strands separate, one serves as a template for messenger RNA (mRNA), the structure that carries information stored on DNA to where proteins are synthesized.
Genes • The human genome consists of approximately 30,000 genes (U.S. Department of Energy, Office of Science, 2009). • Mutations are alterations in the genetic code. They occur rarely. • Differences that occur more frequently are called polymorphisms.
Chromosomes • Genes are organized in a linear fashion along chromosomes. • Chromosome pairs 1 through 22 are called autosomes. • The 23rd pair contains the sex chromosomes: XX in females and XY in males.
Chromosomes(Continued) • Normal male karyotype (National Cancer Institute, 1997)
Chromosomes(Continued) • When the alleles on a pair of chromosomes are identical, the person is called homozygous for the trait. • If the alleles are different, then the person is heterozygous for the trait.
Chromosomes (Continued) • Before a somatic (non-gamete) cell divides, the chromosomes duplicate so that each resulting cell has the original number of 46 chromosomes; this type of cell division is called mitosis. • Meiosis is a two-step cell-division process that occurs in cells that generate sperm and egg cells.
Chromosomes (Continued) • During meiosis, crossing over can allow homologous chromosomes to exchange sections of genetic material; this is called recombination. • During meiosis, a separation error can cause: • Monosomy (resulting zygote has one copy of a chromosome) • Trisomy (resulting zygote has three copies of a chromosome)
Chromosomes (Continued) • Chromosomal abnormalities • Structural—Chromosomal material can break off and attach itself to another chromosome, a process called translocation. • Deletions or duplications of genetic material within a single chromosome • Associated with advanced maternal age
Patterns of Inheritance • Mendelian—Single-gene disorders caused by mutations in a specific gene; can use Mendel’s laws to predict the likelihood of inheritance • Non-Mendelian • Multifactorial—Occur when genes and environmental factors interact
Mendelian: Autosomal Dominant • Only one allele is required to contain a mutation. • A parent has a 50-percent chance of passing the mutation to each offspring. • Examples • Marfan syndrome • Neurofibromatosis • Huntington’s disease
Mendelian: Autosomal Recessive • A mutation is present on both gene copies. • Unaffected carriers can pass the mutation through generations until a carrier mates with another carrier and they have a child with the condition. • Chances that parents carry the same gene mutations increase when they are related through a common ancestor (consanguinity).
Mendelian: Autosomal Recessive (Continued) • Examples • Cystic fibrosis • Factor V Leiden • Tay-Sachs disease
Mendelian: X-Linked Recessive • Genes are located on the X chromosome • Most are recessive. • Examples • Hemophilia A • Duchenne muscular dystrophy • Red-green color blindness
Non-Mendelian: Mitochondrial Inheritance • Women with conditions caused by mutations in mitochondrial DNA pass some of the mutated DNA to their offspring. • Conditions associated with mitochondrial DNA mutations tend to involve skeletal muscle, heart muscle and the brain.
Non-Mendelian: Anticipation • Disorders that become more severe in subsequent generations • Examples • Fragile X syndrome • Myotonic dystrophy • Huntington’s disease
Non-Mendelian: Uniparental Disomy and Imprinting • Uniparental disomy occurs when a child inherits both alleles from a single parent. • Imprinting occurs when genes from each parent are not expressed equally.
Non-Mendelian: Germline Mosaicism • During early development, a mutation may occur in a germline cell (egg or sperm) and pass to descendents of that cell. • Example: Osteogenesis imperfecta
Multifactorial • Examples • Congenital heart defects • Neural tube defects (NTDs) • Diabetes
Family History • The most powerful genetic tool available • Includes a minimum of 3 generations • Constructed as a pedigree that includes: • Ethnicity, culture, religious background • Living or deceased, age at death, cause of death • Physical, mental or developmental conditions
Prenatal Genetic Screening • Identifies if a woman is at higher-than-average risk than other women of having a baby with certain genetic conditions. • Screeing tests include: • Ultrasound • Maternal serum screening • Fetal nuchal translucency • CF screening
Newborn Screening • Newborn screening began in the United States in 1961 with testing for PKU. • State programs test approximately 4 million babies in this country each year; an estimated 5,000 infants are diagnosed with genetic disorders and birth defects annually (Little & Lewis, 2008).
Dysmorphology Assessment • Dysmorphology is the branch of clinical genetics that studies congenital abnormalities. • Providers assess stillborn infants and newborns with dysmorphic features to determine the cause of the malformation (Jones, 2008).
Implications of Genetic Screening for Perinatal Nurses • Nurses must be able to explain the purpose of screening tests and provide clients with information that allows them to make informed decisions about whether to accept or refuse tests as a routine part of prenatal care. • Women who receive positive results need information and support as they decide on a course of action.
Prenatal Genetic Diagnostic Testing • A diagnostic test actually diagnoses or confirms a condition. • Prenatal diagnostic tests include: • Ultrasound • Amniocentesis • Chorionic villus sampling • Carrier testing • Preimplantation diagnosis • Predictive testing
Newborn Genetic Diagnostic Testing • The earlier a diagnosis is made, the earlier treatment can begin. • In some cases, a diagnosis may lead to in-depth genetics education and testing of other family members.
Implications of Genetic Diagnostic Testing for Perinatal Nurses • For clients undergoing genetic diagnostic testing, nurses need to provide safe, effective and culturally appropriate care, including patient education, support, counseling and referral. • Parents need to know the benefits, risks and limitations of genetic diagnostic testing.
Limitations of Genetic Diagnostic Testing • Cannot provide a definitive answer for everyone at risk for an inherited condition. • Cannot always predict the likelihood of a disease • Cannot always predict the severity of a disease
Genetic Diagnostic Testing of Minors • May be useful when the results can contribute to immediate diagnosis and treatment decisions. • If cannot lead to treatment, should be deferred until the child is old enough to provide his own informed consent (AAP Committee on Bioethics, 2001)
Pharmacogenomics • Applies knowledge of the whole genome to the use of pharmaceutical agents, especially as they relate to therapeutic, side and toxic effects (Lewis & Munro, 2010). • By matching the therapeutic agent to a person’s genetic composition, providers may be able to tailor medication, enhance results and minimize or eliminate untoward effects.
Preventing Birth Defects: Preconception Counseling • The goal of preconception counseling is to provide women with information to make timely, informed decisions about future reproduction (Moos, 2003). • Includes: • Family history • Rubella immunity status • Treating chronic health conditions • Carrier testing
Preventing Birth Defects:Folic Acid Supplementation • Folic acid is essential early in pregnancy when fetal tissues and organs are forming. • All women of childbearing age should take 400 micrograms of folic acid daily from a multivitamin or enriched foods (CDC, 2009). • Women who have had a child with an NTD need 4 milligrams of folic acid daily at least 1 month before conception and in the first few months of pregnancy (CDC, 2009).
Managing Risk Factors • Risk assessment includes fetal risk for birth defects and risks to mother and other family members for other conditions • Providers should offer amniocentesis or CVS to women who are carriers of genetic conditions whose partners also are carriers. • Genetic factors associated with PPROM may help prevent preterm birth.
Essential Nursing Competencies • Identifies minimal genetic and genomic competences required of all nurses • Includes professional responsibilities and practice, including: • Nursing assessment • Identification • Referral activities • Education, care and support (Consensus Panel on Genetics/Genomic Nursing Competencies, 2006)
Specialized Genetics Nursing Practice • The ANA recognizes genetics as a nursing specialty and has developed the scope and standards of specialty practice for professional nurses and APNs (ANA & ISONG, 2007). • Nurses can be certified as a genetics clinical nurse (GCN) or an APN in genetics (APNG). APNs also can be certified as genetic counselors.
Integrating Genetics into Nursing Practice: Ethical Principles • ANA’s (2001) Code of Ethics for Nurses with Interpretive Statements guides nursing practice. • Nurses respect for parent choices by: • Supporting parents’ decisions • Ensuring privacy • Respecting parents’ wishes about aspects of care that they can control • Including significant others at the infant’s birth or death, if parents desire
Integrating Genetics into Nursing Practice: Ethical Principles (Continued) • Nurses demonstrate respect for parent choices by: • Supporting parents’ decisions • Ensuring privacy • Respecting parents’ wishes about aspects of care that they can control • Including significant others at the infant’s birth or death, if parents desire
Genetics and the Future • Gene therapy • Human embryonic stem-cell research • Risk profiling based on family history and screening
The Danger of Genetic Determinism: Eugenics • Eugenics is the selective breeding of humans. • The eugenics movement in the United States in the early 20th century included sterilization and immigration laws against people with undesirable traits. • As we reap the benefits of genetic science, we must use the knowledge of genetics wisely.
Conclusion • Perinatal nurses must: • Know about genetics and genomics to provide care to women and infants who have, or who are at risk for having, genetic conditions. • Understand genetic screening and testing to help women, couples and families acquire and understand genetic information. • Support parent care and treatment decisions. • Know the ethical, legal and social implications of genetic technologies.