NU271 PrepU Chapter 5: Genetic and Congenital Disorders
A pregnant client's α-fetoprotein (AFP) returns elevated. The couple ask the health care worker to explain what this means. Which is the best response?
"Elevated AFP means your baby is at risk of having a neural tube defect like spina bifida (an opening in the spine)." Maternal and amniotic fluid levels of AFP are elevated in pregnancies where the fetus has a neural tube defect (i.e., anencephaly and open spina bifida) or certain other malformations such as an anterior abdominal wall defect in which the fetal integument is not intact. Screening of maternal blood samples usually is done between weeks 16 and 18 of gestation. Although neural tube defects have been associated with elevated levels of AFP, decreased levels have been associated with Down syndrome.
A woman who has just learned that she is pregnant for the first time has sought advice from her health care provider about the safe use of alcohol during pregnancy. What advice should the clinician provide to the woman?
"It's likely best to eliminate alcohol from your diet while you're pregnant." Safe intake levels of alcohol during pregnancy are unknown. Even small amounts of alcohol consumed during critical periods of fetal development may be teratogenic. As a result, it is best for pregnant women to forego alcohol use throughout pregnancy.
A mother has one mutant allele on the X chromosome and one normal allele. What is the chance of a daughter to be a carrier of the mutation? A. 75% B. 100% C. 25% D. 50%
50% The common pattern of inheritance is one in which an unaffected mother carries one normal and one mutant allele on the X chromosome. This means that she has a 50% chance of transmitting the defective gene to her sons, and her daughters have a 50% chance of being carrier of the mutant gene. Note that it is not necessary to factor in the odds of the offspring being male or female when calculating the passing of the carrier trait, only the percentage of chance for inheritance for a female offspring.
A newborn has been diagnosed with phenylketonuria (PKU). The nurse teaches the mother about a special diet to restrict phenylalanine intake. When does this diet need to be initiated?
7 to 10 days of age Dietary treatment of PKU must be started early in neonatal life to prevent brain damage. Infants with elevated phenylalanine levels should begin treatment by 7-10 days of age.
Which statement is true about recessive gene inheritance? X-linked recessive genes are expressed only if two X chromosomes are present. Variability of gene expression is called reduced penetrance. Dominant genes have less power of expression than recessive ones. A carrier is a nonaffected person with a single copy of a recessive gene. Exit quiz
A carrier is a nonaffected person with a single copy of a recessive gene. Autosomal recessive disorders are manifested only when both members of the gene pair are affected. Therefore, a carrier is a nonaffected person with a single copy of a recessive gene. Dominant genes have greater expression than recessive ones. Because of the presence of a normal X gene, female heterozygotes rarely experience the effects of a defective gene, whereas all males who receive the gene are typically affected. Variability of gene expression is called variable expressivity.
A clinician who works on a cardiac care unit of a hospital is providing care for a number of clients. Which client most likely has a genetic disorder arising from inheritance of a single gene? A tall, thin, myopic, 28-year-old woman with mitral valve prolapse. An overweight, middle-aged male smoker with coronary artery disease. A short, thin, 56-year-old woman with hypertension. A thin, middle-aged nonsmoking man with a repaired atrial septal defect.
A tall, thin, myopic, 28-year-old woman with mitral valve prolapse. This client exhibits several classic signs of Marfan syndrome, an autosomal dominant genetic disorder of connective tissue. The other clients show signs of heart disease most likely caused by multiple factors.
The gene responsible for a particular congenital cardiac anomaly is said to have complete penetrance. What are the clinical implications of this fact?
All the individuals who possess the gene will exhibit the anomaly. Penetrance represents the ability of a gene to express its function with complete (100%) penetrance, ensuring that all individuals possessing the gene will experience the phenotype in question. The disorder is not necessarily the result of multiple alleles or polygenetic inheritance. Complete penetrance does not mean that the disorder is a single-gene trait.
The gene responsible for a particular congenital cardiac anomaly is said to have complete penetrance. What are the clinical implications of this fact? The anomaly is a result of polygenetic inheritance. All the individuals who possess the gene will exhibit the anomaly. Multiple alleles contribute to the defect. The heart defect does not result from any other gene.
All the individuals who possess the gene will exhibit the anomaly. Penetrance represents the ability of a gene to express its function with complete (100%) penetrance, ensuring that all individuals possessing the gene will experience the phenotype in question. The disorder is not necessarily the result of multiple alleles or polygenetic inheritance. Complete penetrance does not mean that the disorder is a single-gene trait.
Which term is used to describe the process when a child receives two members of a gene pair, one inherited from the mother and the other from the father? Alleles Genotype Locus Phenotype
Alleles Two members of a gene pair, one inherited from the mother and the other from the father, are called alleles. The genes on each chromosome are arranged in pairs and in strict order, with each gene occupying a specific location or locus. Genotype is the genetic makeup, as distinguished from the physical appearance, of an organism or a group of organisms. Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product.
A sonogram on a woman in the first trimester of her pregnancy shows abnormal fetal findings. The nurse prepares to provide the woman with information concerning which diagnostic procedure? Amniocentesis Chorionic villus sampling Biochemical analysis Percutaneous umbilical cord blood sampling
Amniocentesis Amniocentesis is useful in women with elevated risk on first trimester screen or quad screen; abnormal fetal findings on sonogram; or in parents who are carriers or with a strong family history of an inherited disease. Chorionic villus sampling is an invasive diagnostic procedure that obtains tissue that can be used for fetal chromosome studies, DNA analysis and biochemical studies. Percutaneous umbilical cord blood sampling (PUBS) is used for prenatal diagnosis of hemoglobinopathies, coagulation disorders, metabolic and cytogenetic disorders, and immunodeficiencies. Biochemical analyses can be used to detect abnormal levels of AFP and abnormal biochemical products in the maternal blood and in specimens of amniotic fluid and fetal blood.
A nurse notes that a client with neurofibromatosis has eight flat, cutaneous, light brown spots (2 cm in diameter each) over the trunk area. The nurse documents these as being: Plaques Lisch spots Mongolian spots Cafe au lait spots
Cafe au lait spots The nurse should document the light brown, flat, cutaneous spots as being cafe au lait spots.
The provider caring for a 38-year-old pregnant client wants to determine if the child will have Down syndrome. Which prenatal test is used to diagnose this condition?
Chromosome analysis There are several prenatal screening tests that can be done to determine the risk of having a child with Down syndrome. They include nuchal translucency, serum hCG, and serum alpha-fetoprotein. The only way to accurately diagnose the presence of Down syndrome in the fetus is through chromosome analysis using chorionic villus sampling, amniocentesis, or percutaneous umbilical blood sampling.
The nurse teaches a client about the medication classification system used to identify risk for teratogenicity. In which order will the nurse teach the client the categories are placed, from least risk to greatest for teratogenicity?
Class A Class B Class C Class D Class X In 1983 the U.S. Food and Drug Administration established a system for classifying drugs according to probable risks to the fetus. According to this system, drugs are put into five categories: A, B, C, D, and X. Drugs in category A are the least dangerous, and categories B, C, and D are increasingly more dangerous. Those in category X are contraindicated during pregnancy because of proven teratogenicity.
A physician is working with a 30-year-old male client with Down syndrome who has been admitted to hospital with a diagnosis of acute leukemia. Which physical assessment finding would the physician be more likely to find in an examination of this client than other clients without Down syndrome? Congenital heart defects Diabetes mellitus Decreased visual acuity Hepatomegaly
Congenital heart defects Congenital heart defects are associated with Down syndrome. Hepatomegaly, visual disturbances, and diabetes are not associated.
Marfan syndrome is a single-gene disorder that affects which type of tissue?
Connective Marfan syndrome is an autosomal dominant disorder of the connective tissue, which gives shape and structure to other tissues in the body and holds them in place. It affects several organ systems, including the eyes, cardiovascular system and the skeletal system.
Which disease is caused by a genetic defect of chloride transport?
Cystic fibrosis Cystic fibrosis is a single-gene inheritance disorder of membrane transport of chloride ions in exocrine glands, causing lung and pancreatic disease. The other options are also single-gene inheritance disorders but do not involve chloride transport.
A pregnant woman's ultrasound reveals intrauterine growth retardation (IUGR) and a TORCH agent is thought to be the cause. Which nursing action is appropriate? Facilitate serum testing for hepatitis and obtain the client's immunization history. Arrange for the client to be immunized against cholera (Vibrio cholerae). Determine whether the client has been immunized against rubella. Assess whether the client has been exposed to tetanus since becoming pregnant.
Determine whether the client has been immunized against rubella. TORCH stands for toxoplasmosis, other, rubella (i.e., German measles), cytomegalovirus, and herpes. Hepatitis, tetanus, and cholera are not included among lists of TORCH agents.
Is it true or false that prenatal screening can be used to rule out all possible fetal abnormalities? True False
False Prenatal screening cannot be used to rule out all possible fetal abnormalities. It is limited to determining whether the fetus has (or possibly has) designated conditions indicated by late maternal age, family history, or well-defined risk factors.
Which risk factor increases the chances of the development of a neural tube defect during embryonic development?
Folate deficiency Folate deficiency has been closely linked as a risk factor for the development of neural tube defects because folate is needed for the synthesis of amino acids and DNA. It is now recommended that women take folic acid prior to conception to prevent neural tube defects.
Which assessment finding would help support the diagnosis of fetal alcohol syndrome (FAS) in a newborn?
Head circumference below the 10th percentile A head circumference and weight below the 10th percentile are two of the necessary criteria for the diagnosis of FAS. FAS possesses a characteristic set of facial features that includes a thin vermilion border (upper lip), and an elongated, flattened midface and philtrum (i.e., the groove in the middle of the upper lip). Blindness is not necessarily considered a hallmark characteristic of FAS.
The provider is counseling a client who has just been diagnosed with adult polycystic kidney disease, an autosomal dominant disorder. Which statement regarding the transmission of genetic disease is accurate? Healthy or unaffected children are not carriers of the defective gene. The trait will be expressed only if both parents have the gene defect. One affected parent will cause all children to be affected. The trait will be expressed only if the defective gene is carried on the X chromosome.
Healthy or unaffected children are not carriers of the defective gene. Adult polycystic kidney disease is an autosomal dominant disorder. In this disorder, a single mutant allele from an affected parent is transmitted to an offspring regardless of sex. The affected parent has a 50 percent chance of transmitting the disorder to each offspring. The unaffected relative of the parent or unaffected siblings of the offspring do not transmit the disorder.
Mendelian inheritance characteristics are most closely associated with which one of the following? Diabetes mellitus Marfan syndrome Congenital heart disease Turner syndrome
Marfan syndrome Marfan syndrome is an autosomal dominant disorder caused by a mutant allele at a single gene locus and follows Mendelian patterns of inheritance. Congenital heart disease and diabetes mellitus are multifactorial inheritance disorders. Turner syndrome is a chromosomal disorder.
A nurse confers with the attending physician about a client with encephalopathy who has been attributed to mitochondrial gene mutation. Why do mutations of the mitochondria affect the brain?
Mitochondrial mutations affect the ability of tissues to synthesize ATP, and tissues with high demands malfunction without enough ATP. Tissues that have a high demand for the energy provided by ATP malfunction very quickly when ATP cannot be produced fast enough. This includes the brain, the muscular system, the auditory system, and the retina. Mitochondria cannot be silenced by the cell. Mitochondrial proteins and mutations can affect the cell where they reside but not the entire organ.
The tissue that is damaged in Huntington chorea is which of the following?
Nerve tissue Huntington chorea is a neurodegenerative disorder. It does not involve the other types of tissue.
The nurse is teaching a class of pregnant woman about nutrition, emphasizing their need for folic acid. The nurse's rationale for this relates to prevention of which birth defect?
Neural tube defects Folic acid deficiency has been implicated in the development of neural tube defects (anencephaly, spina bifida, encephalocele). Studies have shown a significant decrease in neural tube defects when folic acid was taken long term by women of reproductive age.
An adolescent presents at the clinic with reports of pedunculated lesions projecting from the skin on the trunk area. The nurse knows that this is a sign of: Marfan syndrome Down syndrome Klinefelter syndrome Neurofibromatosis type 1
Neurofibromatosis type 1 In more than 90% of persons with neurofibromatosis type 1, cutaneous and subcutaneous neurofibromas develop in late childhood or adolescence. The cutaneous neurofibromas, which vary in number from a few to many hundreds, manifest as soft, pedunculated lesions that project from the skin. Marfan syndrome affects several organ systems, including the ocular system (eyes), the cardiovascular system (heart and blood vessels), and the skeletal system (bones and joints). Down syndrome is a congenital condition characterized by varying degrees of intellectual disability and multiple defects. Klinefelter syndrome is a condition that occurs in men who have an extra X chromosome in most of their cells. The syndrome can affect different stages of physical, language, and social development. The most common symptom is infertility.
Which diagnostic procedures can be used to collect cells that can be used for fetal karyotyping? Select all that apply. Percutaneous umbilical cord blood sampling Chorionic villus sampling Ultrasound Maternal serum markers Amniocentesis
Percutaneous umbilical cord blood sampling Chorionic villus sampling Amniocentesis Amniocentesis, chorionic villus sampling and percutaneous umbilical cord blood sampling are used to obtain specimens for cytogenetic studies. Cytogenetic studies are used for fetal karyotyping to determine the chromosomal makeup of the fetus. Maternal serum markers are used for biochemical studies. Ultrasonography is used for structural anomalies.
Hearing impairment, blindness, and adverse neurodevelopment in newborns can be prevented by immunization against which childhood disease? Toxoplasmosis Rubella Herpes simplex virus type 2 Epstein-Barr virus
Rubella Although the introduction of the rubella vaccine has virtually eliminated the congenital rubella syndrome in most developed countries, it remains endemic in many developing countries, where it is the major preventable cause of hearing impairment, blindness, and adverse neurodevelopmental outcomes such as cognitive impairment or microcephaly. The other options are infectious agents implicated in fetal anomalies, but do not have vaccines.
Which microorganism can cross the placenta and enter the fetal circulation causing the most frequent fetal anomalies?
Rubella TORCH stands for toxoplasmosis, other, rubella (German measles), cytomegalovirus, and herpes. This acronym can be used to remember the agents most frequently implicated in fetal anomalies. Strep throat, common colds, and the flu can cause concern for the mother but rarely result in fetal anomalies.
The parents of an infant boy ask the nurse why their son was born with a cleft lip and palate. The nurse responds that cleft lip and palate are defects that are caused by many factors. The defect may also be caused by teratogens. Which teratogens can cause cleft lip and palate?
Rubella This defect may be caused by the teratogen rubella and is often encountered in children with chromosomal abnormalities.
Select the screening procedure performed on newborns to decrease the risk of intellectual disability and compromised neurological development. A. Erythromycin eye ointment application B. Vitamin K injection C. Serum glucose test D. Serum phenylalanine test
Serum phenylalanine test Newborn infants are routinely screened within 12 hours of birth for abnormal levels of serum phenylalanine to detect high levels that could cause irreversible intellectual disability. The other procedures that may be performed after birth would not be used as a screening tool for intellectual disability.
Which symptoms support the diagnosis of the autosomal recessive disorder Tay-Sachs disease?
Severe mental deterioration originating in infancy Tay-Sachs disease results in a deficiency of hexosaminidase A that causes severe mental and physical deterioration beginning in infancy. Sickle cell disease is a red blood cell defect. Oculocutaneous albinism causes hypopigmentation of skin, hair, and eyes as a result of the body's inability to synthesize melanin. Cystic fibrosis is a disorder of membrane transport of chloride ions in exocrine glands causing lung and pancreatic disease.
What will likely be the outcome when a male child inherits an X-linked disorder from his heterozygous carrier mother? His sons will be carriers. Some of his sisters will be carriers. His father has the disorder. His daughters will have the disorder.
Some of his sisters will be carriers. A male who has a recessive X-linked disorder will have daughters who are carriers and sons who are unaffected. Male children of a carrier mother have a 50% risk of having the disorder and cannot be carriers. Female children of a carrier mother have a 50% risk of being carriers and are not affected by the disorder.
Which condition follows a Mendelian pattern of recessive inheritance? Down syndrome Tay-Sachs disease Marfan syndrome Coronary artery disease
Tay-Sachs disease Tay-Sachs disease is an autosomal recessive disorder of Mendelian or single-gene inheritance. Coronary artery disease is a multifactorial inheritance disorder. Down syndrome is a numeric disorder involving autosomes. Marfan syndrome follows Mendelian inheritance but is autosomal dominant.
The nurse is assessing a newborn. What characteristic finding makes the nurse suspect the newborn has trisomy 21? Large, protruding ears Thin lips and small tongue Long fingers with extra creases Upward slanting of eyes
Upward slanting of eyes Newborns with Down syndrome have short stubby fingers and a single palmar crease (simian crease). The other distinctive features include upward slanting eyes, protruding tongue, and low-set little ears.
Which disease is caused by a genetic defect of chloride transport? von Willebrand disease Cystic fibrosis Phenylketonuria Spherocytosis
Von Recklinghausen disease A second major component of type 1 neurofibromatosis, or von Recklinghausen disease, is the presence of large, flat cutaneous pigmentations known as café au lait spots. A Wood lamp, which uses ultraviolet light, can be used to detect lighter spots. The other options are chromosomal disorders and do not exhibit these pigmentations.
While examining a client, the practitioner notices large, flat, cutaneous pigmentations. They are a uniform light brown with sharply demarcated edges. He uses a Wood lamp to better detect the lighter spots. The practitioner knows that the pigmentations may be a component of which disorder?
Von Recklinghausen disease A second major component of type 1 neurofibromatosis, or von Recklinghausen disease, is the presence of large, flat cutaneous pigmentations known as café au lait spots. A Wood lamp, which uses ultraviolet light, can be used to detect lighter spots. The other options are chromosomal disorders and do not exhibit these pigmentations.
The nurse is caring for a client who was just told she is 4 months pregnant and was unaware of the pregnancy. The nurse is reviewing any medications that the client may have taken in the past 5 months. Which characteristic of the medication(s) will the nurse assign the most significance when considering if the medication may be teratogenic? How long the client took the drug prior to becoming pregnant If the drug was a prescribed or taken without prescription Whether the medication is lipid or water-soluble The route of the medication (oral, transdermal, or parenteral)
Whether the medication is lipid or water-soluble If the medication is lipid-soluble, it passes through the placenta more readily than water-soluble medications. This will be the factor with the most significance for the nurse when taking a health history. Prescription drugs such as antiepileptic drugs are teratogenic. Vitamin A, which is obtained without a prescription, is also a suspected teratogen, but this is not as important a characteristic. The route of administration will not alter the teratogenic effects. Though it will be good to know how long the client has taken the medication, this does not tell us if that particular medication is more likely to be teratogenic or not.
The parents of a newborn are relieved that their baby was born healthy, with the exception of a cleft lip that will be surgically corrected in 10 to 12 weeks. Which statement by the nurse to the parent's best conveys the probable cause of the newborn's cleft lip? "A cleft lip can sometimes result from taking prescription drugs, even when they are taken as prescribed." "Your newborn's cleft lip likely results from the interplay between environment and genes." "Though you are both healthy, you likely both carry the gene for a cleft lip." "Provided one of you had the gene for a cleft lip, your baby likely faced a 50/50 chance of having one."
Your newborn's cleft lip likely results from the interplay between environment and genes." A cleft lip is considered to be a multifactorial disorder, in which both environment and genes contribute to the condition. It does not depend solely on Mendelian patterns of inheritance. A cleft lip is not known to result from teratogenic drugs.
A client goes to radiology for a series of x-rays. As the lead apron is placed over the client, he asks why it is needed. The client should be told that the vest is to protect:
against chromosomal breakage. X-rays have been shown to cause chromosomal breakage and lead to rearrangement and mutation; they do not directly affect the cytoplasm. Proteins and lipids may be altered by X-rays, but they are quickly degraded and removed and therefore have no effect.
The nurse is explaining congenital defects to a newly pregnant client. She explains that one of the most common birth defects is: pyloric stenosis. congenital heart disease. cleft lip with or without cleft palate. spina bifida.
cleft lip with or without cleft palate. Cleft lip with or without cleft palate is one of the most common birth defects. Other congenital defects that are thought to arise through multifactorial inheritance are clubfoot, congenital dislocation of the hip, congenital heart disease, pyloric stenosis, and urinary tract malformation.
Unlike other teratogens, alcohol exposure during pregnancy (fetal alcohol spectrum disorders) can have what harmful effect on the fetus?
developmental abnormalities throughout the prenatal and postnatal period Unlike other teratogenic exposures that cause abnormalities during a short period of time during fetal development (usually in the early weeks), fetal alcohol spectrum disorders (FASD) damage the chromosomes of the developing fetus as long as alcohol continues to circulate through the fetal bloodstream. FASD is diagnosed by the presence of three findings that do not include liver abnormalities and are not life threatening. Facial features characteristic of FASD are most noticeable during childhood. The facial features of FASD may not be as apparent in older people. Each defect can vary in severity, probably reflecting the timing of alcohol consumption in terms of the period of fetal development, amount of alcohol consumed, and hereditary and other environmental influences.
A young man has been diagnosed with Huntington disease following several months of progressive muscle weakness. The man has two young children: one boy and one girl. The nurse should teach the man that: the girl will develop Huntington disease after puberty. each child has 50% chance of developing Huntington disease. both children will develop Huntington disease because it is autosomal dominant. the children have an increased risk of Huntington disease, but the risk is unknown because the disease is multifactorial.
each child has 50% chance of developing Huntington disease. In a single-gene autosomal dominant disease such as Huntington disease, the affected parent has a 50% chance of transmitting the disorder to each offspring. Sex-linked differences do not exist and, because it is a single-gene disorder, the cause is not multifactorial.
The most critical time for teratogenic influence in embryonic development is: from conception to day 15. from day 90 to day 120 after conception. from day 60 to 90 after conception. from day 15 to day 60 after conception.
from day 15 to day 60 after conception. The embryo's development is most easily disturbed during the period when differentiation and development of the organs are taking place. This time interval, which is often referred to as the period of organogenesis, extends from day 15 to day 60 after conception.
The nurse is studying genetic disorders. She learns that an allele is:
one of two members of a gene pair, for a particular trait, in a chromosome pair. The two members of a gene pair, one inherited from the mother and the other from the father, are called alleles. The presence of more than two chromosomes to a set is called polysomy. The physical trait associated with a particular gene is the phenotype.
Teratogenic substances cause abnormalities during embryonic and fetal development. These substances have been divided into three classes. These classes are called:
radiation; drugs and chemical substances; and infectious agents. Teratogenic agents have been divided into three groups: radiation; drugs and chemical substances; and infectious agents. The period of organogenesis, the third trimester, and the second trimester are not teratogenic substances. They are time periods during the pregnancy. Teratogenic substances are not classified as outside, inside, or internal. Although drugs and chemical substances are a class of teratogenic agents, smoking is included in that class as a teratogenic agent. It is not a class unto itself. Bacteria and viruses are considered infectious agents and are therefore teratogenic agents.
