Genetics and Genetic Counseling PDF

NUR C202 Care of Mother and Child at Risk or with Problems (Acute and Chronic) By Gina M. Dumawal RN, MAN  Genetics and Genetic Counseling  OBJECTIVES At the end of the session, the students will be able to; 1. Describe the nature of inheritance,...

NUR C202 Care of Mother and Child at Risk or with Problems (Acute and Chronic) By Gina M. Dumawal RN, MAN  Genetics and Genetic Counseling  OBJECTIVES At the end of the session, the students will be able to; 1. Describe the nature of inheritance, patterns of recessive and dominant mendelian inheritance, and common chromosomal aberrations that cause physical or cognitive disorders. 2. Assess a family for their adjustment to the probability of inheriting a genetic disorder. 3. Formulate nursing diagnoses related to genetic disorders. 4. Plan nursing care related to a potential alteration in genetic health, such as assisting with an amniocentesis. 5. Implement nursing care such as counseling a family with a genetic disorder. 6. Evaluate expected outcomes for achievement and effectiveness of care. 7. Integrate knowledge of genetic inheritance with nursing process Genetics  Introduction to Genetics GENETICS – branch of science, studies genes & pattern of inheritance of particular diseases. Chromosomes - carry the hereditary information (genes). Genes - basic units of inheritance that determine both the physical and cognitive characteristics of people. DNA - forms the genetic material. Genomics - address the functions and interactions of all the genes in an organisms. It is the study of the entire DNA structure.  Introduction to Genetics Genome - the complete copy of genetic material in an organism (about 50,000 to 100,000). * A normal genome is abbreviated as 46XX or 46XY. If a chromosomal aberration exists, it is listed after the sex chromosome pattern (Down syndrome - extra chromosome 21, abbreviated as 47XX21 or 47XY21. Phenotype - the person’s outward appearance. Genotype - the person’s actual gene composition. ▪ Homozygous – a person who has two like genes for a trait on two like chromosomes. ▪ Heterozygous – if the genes differ (a healthy gene from the mother and an unhealthy gene from the father, or vice versa). Inherited or genetic disorders - can be passed from one generation to the next.  Introduction to Genetics Karyotype is the schematic arrangements of the chromosomes within a cell to demonstrate their numbers and morphology * hereditary = derived from parents * familial = transmitted in the gametes through generations * congenital = present at birth (not always genetically determined - e.g. congenital syphilis, toxoplasmosis)  Introduction to Genetics In humans, each cell contains 46 chromosomes (22 pair of autosomes and 1 pair of sex chromosomes). Spermatozoa and ova each carry only half of the chromosome number, or 23 chromosomes. For each chromosome in sperm cell, there is a like chromosome of similar size, shape & function (autosome, or homologous chromosome) in ovum. Two like genes (alleles) for every trait are represented in the ovum and sperm on autosomes. The one chromosome in which this does not occur is the chromosome for determining gender.  Genetic Inheritance of a Disease Multifactorial (Polygenic) Inheritance Appears to occur from multiple gene combinations possibly combined with environmental factors. A family history, for instance, may reveal no set pattern. Some of these conditions have a predisposition to occur more frequently in one sex (cleft palate occurs more often in girls than boys), but they can occur in either sex.  Risk Factors for Genetic Disorders Factors that increase your risk of having a baby with a genetic disorder include: Family history of a genetic disorder Prior child with a genetic disorder One parent has a chromosomal abnormality Advanced maternal age (35 or older) Advanced paternal age (40 or older) Multiple miscarriages or prior stillbirth It is important to know that some birth defects, developmental delays, and/or illnesses can be caused by prenatal exposure to drugs, alcohol, or other environmental factors.  Types of Disorders that can be Seen During Pregnancy Single gene disorders occur when a change in one gene causes a disease. Examples include cystic fibrosis, sickle cell anemia, and hemophilia. Chromosomal abnormalities occur where there are missing or extra chromosomes, or pieces of chromosomes. Down syndrome, the most common chromosomal abnormality, is caused by an extra chromosome number 21. Chromosome abnormalities can be inherited from a parent or they can happen by chance. Multifactorial or complex disorders are caused by a combination of genetic predispositions and environmental factors, which makes it harder to predict who may be at risk. Examples include heart defects, cleft lip or cleft palate, and spina bifida.  Types of Disorders that can be Seen During Pregnancy Teratogenic disorders occur when the baby is exposed to substances during pregnancy that cause abnormalities, otherwise known as “teratogens.” Babies are very sensitive in the first trimester, when all of the organs are developing. Teratogens include alcohol, drugs, lead, high levels of radiation exposure, and certain medications, infections and toxic substances. Testing for Genetic Disorders 1. Screening tests – check the risk of your baby having certain genetic disorders. 2. Diagnostic tests – can detect if certain genetic disorders are actually present in the baby. ❖Screening and diagnostic tests are optional. They are available to all women, even those who do not have any known risk factors.  Testing for Genetic Disorders Screening Tests - to check the chance of your baby having certain genetic disorders include: Carrier screening - blood test that tries to determine if either parent carries a genetic change for inherited disorders that could be passed on to the baby, can be performed on a saliva sample, best time to be done before getting pregnant, but it can be done during pregnancy as well. Prenatal genetic screens - series of first and second trimester screens that use blood samples from the mother as well as ultrasounds to check the baby’s risk of having certain common genetic disorders. Examples include Down syndrome and certain birth defects, such as spina bifida. Noninvasive Prenatal Testing (NIPT) or cell-free DNA screening - blood test that checks DNA from the placenta that is found in the mother’s blood. This screens for the most common chromosome abnormalities, such as Down syndrome and trisomy 18, and is most commonly used in high-risk pregnancies.  Testing for Genetic Disorders Diagnostic Tests - performed during pregnancy to detect if certain genetic disorders are present in the baby, such as cystic fibrosis or Down syndrome. Diagnostic tests are generally safe procedures when performed by an experienced physician. Routine diagnostic tests include: Chorionic villus sampling - tests a sample of tissue taken from the placenta in the first trimester. Amniocentesis - tests a sample of the amniotic fluid taken from the womb in the second trimester  Testing for Genetic Disorders Additional advanced diagnostic tests and technologies available include: Fetal blood sampling or percutaneous umbilical blood sampling (PUBS) uses a blood sample from the baby’s umbilical cord to test for genetic disorders. This is usually done when amniocentesis or chorionic villus sampling are not possible. Prenatal Chromosome Analysis (Karyotype) is a common genetic test performed on cells obtained from an amniocentesis or CVS that can detect large changes in the chromosomes, such as an extra or missing chromosome or a change in how the chromosomes are put together. Prenatal Chromosomal Microarray Analysis (CMA) is a more detailed test performed on cells obtained from an amniocentesis or CVS and tries to detect if any pieces of chromosomes are missing or extra. These extra or missing pieces may be too small to see on a karyotype alone. Fetal genomic or whole-exome sequencing (WES) is a diagnostic test for pregnancies with complex fetal conditions that checks almost all of a baby’s genes.  Genetic Counseling If you are pregnant or planning a pregnancy, you may be referred to a genetic counselor to: Assess your personal risk of having a baby with a genetic disorder. Review your testing options. Coordinate genetic screenings and diagnostic tests and interpret the results. Provide emotional support and educational resources for you and your family. Help you make informed decisions about your pregnancy and your baby’s treatment, and prepare for appropriate medical care.  Treatment for Fetal Genetic Disorders Treatment depends on the genetic disorder and the individual pregnancy. In general, if your baby is diagnosed with a genetic disorder during pregnancy your treatment will include: Specialized care from a maternal-fetal medicine physician. Individualized care based on the genetic disorder, your pregnancy, and your family’s preferences. Treatment options ranging from medical therapy during pregnancy, such as fetal interventions, to surgery immediately after birth. A multidisciplinary, collaborative healthcare team, including genetic counselors, imaging specialists, fetal specialists, fetal and neonatal surgeons as needed, and neonatologists and pediatricians experienced in the treatment of children with genetic disorders Support services for you and your family. End of Slides