Ch. 6 PrepU

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?

"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 woman homozygous for the gene mutation that causes cystic fibrosis, with a partner who does not carry the same mutation, has what chance of having a child with the disease?

0% chance Cystic fibrosis is a single-gene autosomal recessive disorder. Autosomal recessive disorders are manifested only when both members of the gene pair are affected. Since her partner does not carry the gene, both members of the gene pair cannot be affected and she has a zero percent chance of having a child with the disease.

The physician suspects a client may have Klinefelter syndrome. To confirm the diagnosis, the chromosome pattern would identify:

47, XXY Most males with Klinefelter syndrome have one extra X chromosome (47, XXY), and in rare cases, there may be one additional extra X chromosome (48, XXXY).

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.

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.

With increasing age comes a greater chance of a woman having been exposed to damaging environmental agents such as drugs, chemicals, and radiation. These factors may act on the aging oocyte to cause which abnormality in a fetus?

Down syndrome The risk of having a child with Down syndrome increases with maternal age—it is 1 in 1250 at 25 years of age, 1 in 400 at 35 years, and 1 in 100 at 45 years of age. The reason for the correlation between maternal age and nondisjunction is unknown, but is thought to reflect some aspect of aging of the oocyte. Although males continue to produce sperm throughout their reproductive life, females are born with all the oocytes they ever will have. These oocytes may change as a result of the aging process. With increasing age, there is a greater chance of a woman having been exposed to damaging environmental agents such as drugs, chemicals, and radiation. There is no correlation with maternal age and the other syndromes.

The nurse teaches the pregnant radiation technologist that excessive levels of radiation have been shown to cause which conditions? Select all that apply.

Intellectual disability Microcephaly Skeletal malformations Heavy doses of ionizing radiation are teratogenic and mutagenic and have the capacity to effect inheritable changes in genetic material. Specifically, excessive levels of radiation have been shown to cause microcephaly, skeletal malformations, and intellectual disability. The other options are single-gene inheritance disorders.

The most critical time for teratogenic influence in embryonic development is:

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.

When a client exposed to a teratogenic agent during the seventh week of pregnancy asks the nurse how this might that impact the fetus's development, which would be the most accurate response?

"The external genitalia may be impacted." The nurse should respond that the external genitial may be impacted, as they are sensitive to teratogenic agents during this period of embryogenesis.

A pregnant woman is concerned about acquiring toxoplasmosis. The most important information for the nurse to give the client would be:

"Do not clean your cat's litter box." The domestic cat can carry Toxoplasma gondii, excreting the protozoa in its feces. It has been suggested that pregnant women should avoid contact with excrement from the family cat. The infection can be contracted by eating raw or inadequately cooked meat or food that has come in contact with infected meat. Thus, raw and rare meat should be avoided.

The nurse is providing education to the parent of a male diagnosed with Marfan syndrome. The nurse knows that her teaching has been effective when the parent states which of the following?

"His participation in sports may need to be limited." Marfan syndrome affects several organ systems, including the eyes, cardiovascular, and skeletal systems. The risks associated with participation in sports depend on which organ system is involved. There is no cure for Marfan syndrome and the most life-threatening aspects of the disorder are the cardiovascular defects.

A male client has an autosomal dominant disorder. The client and his partner are considering starting a family. Which statement indicates the client has an adequate understanding of the genetic basis of this health problem?

"I know that a single mutant allele is to blame for the health problem." Autosomal dominant disorders are the result of a single mutant allele from an affected parent. There is a 50% risk of transmission, and unaffected people do not pass on the disorder. New genetic mutations may occur between generations.

A couple who are pregnant with their first child have made an appointment with a clinical geneticist to discuss prenatal screening. The man states that they "just want to make sure that there is nothing wrong with our baby." How could the clinician best respond to this statement?

"Testing the umbilical blood and performing amniocentesis can give us some information but not a guarantee." Prenatal screening provides a useful but incomplete picture of fetal health; umbilical sampling and amniocentesis are common methods of screening. Fetal-tissue biopsy is a rarely used screening method, and a couple need not belong to a high-risk group to benefit from prenatal screening. Abnormalities do not usually necessitate termination.

A couple who are pregnant with their first child have made an appointment with a clinical geneticist to discuss prenatal screening. The man states that they, "just want to make sure that there is nothing wrong with our baby." How could the clinician best respond to this statement?

"Testing the umbilical blood and performing amniocentesis can give us some information, but not a guarantee." Prenatal screening provides a useful, but incomplete, picture of fetal health; umbilical sampling and amniocentesis are common methods of screening. Fetal tissue biopsy is a rarely-used screening method, and a couple need not belong to a high-risk group to benefit from prenatal screening. Abnormalities do not usually necessitate termination.

Both members of a couple are carriers of an autosomal recessive trait. What will the nurse teach the couple about the risk of their child being affected?

"There is a 25% chance the child will be affected with the disease trait." Autosomal recessive disorders include almost all inborn errors of metabolism, with deficiencies of enzymes rather than abnormal protein structure. Age of onset tends to be early in life. There is a two-in-four chance of having a child who is a carrier, but only a 25% risk for having an affected child. Phenylketonuria (PKU) is a rare autosomal recessive metabolic disorder that affects approximately 1 in every 10,000 to 15,000 infants in the United States. Infants with the disorder are treated with a special diet that restricts phenylalanine intake. If untreated, the disorder results in intellectual disability, microcephaly, delayed speech, and other signs of impaired neurologic development. Tay-Sachs disease is inherited as an autosomal recessive. Infants with Tay-Sachs disease appear normal at birth but begin to manifest progressive weakness, muscle flaccidity, and decreased responsiveness at approximately 6 to 10 months of age. The occurrence risks in each pregnancy (with both parents being carriers) are one in four (25%) for an affected child and two in four (50%) for a carrier child.

The mother of a child with Turner syndrome asks the nurse what the physician meant when the disease was explained as monosomy of the X chromosome. The nurse explains the syndrome as having which of the following characteristics?

"There is one X chromosome." The nurse should explain that there is one X chromosome instead of the normal two X chromosomes (one from each parent).

As part of her prenatal care, a pregnant woman and her partner are being taught by a community health nurse. Which point about the teratogenic effects of different substances should the nurse include in teaching?

"Your developing baby is most vulnerable during the first 2 months of your pregnancy." The period between days 15 and 60 is the most susceptible time during development. Vitamin A, not D, poses a particular risk, and only 2% to 3% of anomalies are attributable to drug and environmental factors. It is not necessary to categorically avoid medication, but rather to use caution and heed FDA guidelines.

Which statement is true about recessive gene inheritance?

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. 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.

Which pregnant woman has most likely encountered the greatest increase in the risk that her child will have a fetal anomaly?

A woman who has herpes simplex and who has recently recovered from endocarditis. Herpes is among the microorganisms most commonly responsible for fetal anomalies. Syphilis and tuberculosis infections are also implicated but to a lesser degree. The other listed diagnoses are not noted to be associated with fetal anomalies.

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?

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.

The nurse is planning care for a 6-hour-old neonate who has been born with cleft palate. What aspect of care should the nurse prioritize?

Adequate nutrition The immediate problem in an infant with cleft palate is feeding; the nurse should therefore focus on ensuring the neonate achieves adequate nutrition, which may require adaptive feeding equipment and approaches. A neonate does not have a body image. Though the parents may experience anxiety, the nurse will manage this while ensuring adequate nutrition. Though infants with cleft palate are at greater risk for ear infections (otitis media), this will not develop as a concern as readily as malnutrition or dehydration in these first few days of life. Proper feeding techniques can also reduce this risk for otitis media.

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 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 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.

The criteria for fetal alcohol syndrome diagnosis require the documented presence of all of the following except which one?

An absence of all or part of the X chromosome An absence of all or part of the X chromosome is seen in Turner syndrome. The other options are criteria for fetal alcohol syndrome diagnosis.

The nurse is studying numeric disorders involving autosomes. Which term refers to having an abnormal number of chromosomes?

Aneuploidy Having an abnormal number of chromosomes is referred to as aneuploidy. When a person inherits a dominant mutant gene, but fails to express it, the trait is described as having reduced penetrance. In mitochondrial gene disorders, some cells receive a mixture of normal and mutant DNA, known as heteroplasmy. Occasionally, mitotic errors in early development give rise to two or more cell lines characterized by distinctive karyotypes, a condition referred to as mosaicism.

A woman gave birth to a small infant with a malformed skull. The infant grows slowly and shows signs of substantial cognitive and intellectual deficits. The child also has facial abnormalities that become more striking as it develops. What might the nurse expect to find in the mother's pregnancy history?

Chronic alcohol use The infant's signs and symptoms are characteristic of fetal alcohol syndrome. Folic acid deficiency is associated with neural tube defects, such as anencephaly and spina bifida. Cocaine use is associated with some of the same signs and symptoms as alcohol use but does not produce the characteristic facial abnormalities of fetal alcohol syndrome. Herpes simplex infection, although it is associated with microcephaly, hydrocephalus, defects of the eye, and hearing problems, also does not produce characteristic facial abnormalities.

The U.S. Food and Drug Administration established a system in 1979 for classifying drugs according to their proven teratogenicity. Place these classes of drugs in order from least to greatest potential for teratogenicity.

Class A Class B Class C Class D Class X In 1979, 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.

Abnormalities of body structure, function, or metabolism that are present at birth are known as:

Congenital Congenital defects, sometimes called birth defects, are abnormalities of body structure, function, or metabolism that are present at birth. A teratoid is a chemical, physical, or biologic agent that produces abnormalities during embryonic or fetal development. Neonatal refers to the period of time that is 28 days after birth. Premature is the state of an infant being born prior to completion of the 37th week of gestation.

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 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.

Maternal serum alpha-fetoprotein (AFP) is a screening test for which condition?

Down syndrome There are several prenatal screening tests that can be done to determine the risk of having a child with Down syndrome. The most commonly used are blood tests that measure maternal serum levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol, inhibin A and pregnancy-associated plasma protein A (PAPP-A). AFP is not a screening test for the other conditions.

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.

An 11-year-old girl is suspected of having Turner syndrome. Which diagnostic test would be the most useful component of screening to confirm or rule out the diagnosis?

Echocardiogram Because of the association between congenital heart defects and Turner syndrome, an echocardiogram would be most likely to yield useful results. Turner syndrome is not associated with brain, skeletal, or liver involvement and these tests would be less likely to provide useful insight.

Which action is an appropriate intervention by a nurse working with the parents of an infant newly diagnosed with Tay-Sachs disease?

Encourage parents to verbalize fears and feelings. The nurse should encourage the parents to verbalize their feelings and fears related to the infant's diagnosis to promote psychosocial integrity. Tay-Sachs is not curable and the life expectancy of children diagnosed with it is 4-5 years. Teaching the efficacy of a low-protein diet, keeping the infant's head elevated after meals, and/or administering IV antibiotics will not impact the course of the disease.

After studying genetic disorders, the pathophysiology student knows that which of the following is true?

Genotype determines phenotype. The genetic compostion of a person is called a genotype, whereas the phenotype is the observable expression of a genotype. Diabetes mellitus is caused by a multifactorial inheritance disorder and sickle cell anemia by a single gene defect. Many diseases caused by a single-gene defect have been identified.

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.

While taking a daily walk, the nurse is asked by a neighbor what centric fusion (Robertsonian) translocation means. The neighbor tells the nurse that a family member has been diagnosed with this and is now afraid to have children. Given this diagnosis, what may be potential risks for her offspring?

If chromosome 21 is involved, there is a high risk for producing a child with Down syndrome. In centric fusion or Robertsonian translocation, the break occurs near the centromere affecting the short arm in one chromosome (13 and 14, or 14 and 21 most commonly). The short fragment is usually lost during subsequent divisions. In this case, the person has only 45 chromosomes, but the amount of genetic material lost is small. Difficulty arises during meiosis. The chief clinical significance arises when the translocation carriers involve chromosome 21, which may produce a child with Down syndrome.

The nurse is caring for an 8-month-old male client who has just been diagnosed with hemophilia A. The parents ask about the likelihood that any future children would be born with the condition. What is the nurse's best response?

If you have another son there is a 50% chance that he will also have hemophilia. Hemophilia A is an x-linked recessive condition; thus, the defective gene is only expressed in males who inherit the affected X chromosome from the mother. Females will only be carriers of the condition if they receive the affected X chromosome from the mother. Therefore, only if the couple have a second son will there be a 50% chance the child will have hemophilia; this chance does not change because the first son has the condition. Though it is true the severity can vary, the nurse should be clear that only male children will develop the condition. The nurse should not dismiss the question outright since the inheritance pattern of this condition is well known.

While teaching a client, the nurse should emphasize which information about an autosomal dominant disorder?

It has variation in gene penetration and expression. Autosomal dominant disorders are characterized by variable gene penetrance (degree to which the trait is displayed) and expression (differences in how the trait is displayed). Aneuploidy is not a single-gene disorder and does not follow the Mendelian pattern of inheritance. Deficiencies of enzyme synthesis are common in autosomal recessive disorders. X-linked inheritance can be dominant or recessive but it is not autosomal.

The nurse is assessing a prepubertal male with fragile X syndrome. Assessment findings would include:

Large testes The most distinctive feature that is present in 90% of prepubertal males with fragile X syndrome is macroorchidism or large testes. Someone with fragile X syndrome typically has a long face with large mandible and large, everted ears. Cleft palate is not associated with fragile X syndrome.

The nurse is learning about mitochondrial DNA mutations. She learns that they generally affect which tissues and organs?

Neuromuscular Mitochondrial DNA mutations generally affect tissues that are dependent on oxidative phosphorylation to meet their high needs for metabolic energy. Thus, mtDNA mutations frequently affect the neuromuscular system and produce disorders such as encephalopathies, myopathies, retinal degeneration, loss of extraocular muscle function, and deafness.

A nurse caring for a child with type 1 neurofibromatosis notes that the child has pigmented nodules of the iris. Which of the following is the nurse reporting?

Lisch nodules The nurse should report the pigmented nodules of the iris in a child with type 1 neurofibromatosis as Lisch nodules.

Mendelian inheritance characteristics are most closely associated with which one of the following?

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:

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 condition is characterized by a deficiency of the liver enzyme phenylalanine hydroxylase?

Phenylketonuria Phenylketonuria (PKU) is a rare metabolic disorder that affects approximately 1 in every 15,000 infants in the United States. The disorder, which is inherited as a recessive trait, is caused by a deficiency of the liver enzyme phenylalanine hydroxylase. As a result of this deficiency, toxic levels of the amino acid phenylalanine accumulate in the blood and other tissues. Tay-Sachs disease is a variant of a class of lysosomal storage diseases, known as the gangliosidoses, in which there is failure of lysosomes to break down the GM2 ganglioside of cell membranes. Cystic fibrosis is the production of abnormally thick mucus, leading to the blockage of respiratory and glandular ducts. Cri du chat is a syndrome involving chromosome 5.

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.

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.

Ultrasonography is most likely to detect which fetal abnormality?

Skeletal abnormalities Ultrasonography allows the visualization of body structures, revealing such defects as skeletal malformations. It is only able to identify chromosomal disorders, genetic disorders, and neural tube defects by way of their anatomic effects.

After attending a preconception workshop, a young woman asks the educator to explain neural tube defects (NTD). Which conditions are examples of neural tube defects? Select all that apply.

Spina bifida Anencephaly Encephalocele Folic acid deficiency has been implicated in the development of neural tube defects (e.g., anencephaly, spina bifida, encephalocele). Cleft palate and heart defects are not associated with neural tube defects.

The health care provider is assessing a 6-month-old infant. The parents state that the child appeared normal at birth and in the first few months; however, they have seen the following changes in their infant: progressive weakness, muscle flaccidity, and decreased attentiveness. The health care provider suspects:

Tay-Sachs Disease Infants with Tay-Sachs disease appear normal at birth but begin to manifest progressive weakness, muscle flaccidity, and decreased attentiveness at approximately 6 to 10 months of age. This is followed by rapid deterioration of motor and mental function, often with development of generalized seizures. Retinal involvement leads to visual impairment and eventual blindness. The disease is invariably fatal, and death usually occurs before 4 to 5 years of age.

Which condition follows a Mendelian pattern of recessive inheritance?

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.

A pregnant client is just completing her first trimester and has opted for alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) testing. The nurse should identify what implication from this client's decision?

The client wishes to know about her fetus' risk of having a trisomy. AFP and hCG testing are most often performed to determine the risks of a trisomy. Multifactorial disorders are not revealed by this form of testing and the nurse should not presume that the client will choose to have an abortion if the results are positive. The use of AFP and hCG testing does not preclude the use of amniocentesis.

The nurse is caring for a client who tried to become pregnant but suffered a spontaneous abortion (miscarriage) during her first trimester. What is the most likely etiology of the client's abortion?

The fetus had a chromosomal disorder. Chromosomal abnormalities are thought to cause around half of first-term abortions. For most women, this possibility is a much more likely cause of abortion than radiation or toxins. X-linked disorders are not thought to be a major cause of spontaneous abortion.

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:

The nurse should document the light brown, flat, cutaneous spots as being cafe au lait spots.

The embryo is most susceptible to adverse influences during the period from 15 to 60 days after conception. Which term is used to describe this period?

The period of organogenesis 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. There are no periods of susceptibility, fetal anomalies, or hormonal imbalance.

The genetic counselor is explaining structural changes in chromosomes that result from breakage and rearrangement of chromosome parts. The pattern that occurs when there are simultaneous breaks in two chromosomes, from different pairs, with exchange of chromosome parts is:

Translocation Translocation occurs when there are simultaneous breaks in two chromosomes, from different pairs, with exchange of chromosome parts. Isochromosome formation occurs when the centromere, or central portion, of the chromosome separates horizontally instead of vertically. Ring formation results when deletion is followed by uniting of the chromatids to form a ring. Inversion requires two breaks on a single chromosome with inversion to the opposite side of the centromere or with the fragment inverting but remaining on the same arm.

The provider is doing genetic counseling with a client. He explains that which condition affects only females?

Turner syndrome Turner syndrome describes an absence of all (45, X/0) or part of the X chromosome and, as such, is seen only in females. Klinefelter syndrome is a condition of testicular dysgenesis accompanied by the presence of one or more extra X chromosomes in excess of the normal XY complement. Most males with Kleinfelter syndrome have one extra X chromosome (47, XXY). Down syndrome, trisomy 21, can be seen in either sex. Fragile X syndrome, as with other X-linked disorders, affects boys more often than girls.

The provider receives fetal karyotype results on one of h is clients. The karyotype describes an absence of all or part of the X chromosome. Which condition does the fetus exhibit?

Turner syndrome Turner syndrome is caused by an absence of all or part of the X chromosome. Down syndrome is a trisomy 21. Klinefelter syndrome is a condition of testicular dysgenesis accompanied by the presence of one or more extra X chromosomes in excess of the normal XY complement. Achrondroplasia is a single-gene inheritance disorder.

The provider receives fetal karyotype results on one of his clients. The karyotype describes an absence of all or part of the X chromosome. Which condition does the fetus exhibit?

Turner syndrome Turner syndrome is caused by an absence of all or part of the X chromosome. Down syndrome is a trisomy 21. Klinefelter syndrome is a condition of testicular dysgenesis accompanied by the presence of one or more extra X chromosomes in excess of the normal XY complement. Achrondroplasia is a single-gene inheritance disorder.

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.

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.

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:

each child has 50% chance of developing Huntington disease. In a single-gene autosomal dominant disease such as Huntington, the affected parent has a 50% chance of transmitting the disorder to each offspring. Sex-linked differences do not exist.

The nurse explains to prospective parents that AA or aa in a Punnett square represent two alleles of a given pair that are the same, or:

homozygotes. When two alleles of a given pair are the same as in AA or aa, they are considered homozygotes.

A nurse is caring for an infant born with a cleft lip and palate. The priority of care would address:

malnutrition. The immediate problem in infants with cleft lip and palate is feeding because of their inability to suck to breast-feed or drink from a bottle. The others will be of concern at a later time and are not life threatening.

Fortification of foods with folic acid has resulted in a significant reduction in the incidence of:

neural tube defects. Folic acid deficiency has been implicated in the development of neural tube defects. Huntington disease is an autosomal dominant disorder. Turner syndrome is a chromosomal disorder. Cleft lip and palates are multifactorial inheritance disorders.

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.