EAQ 1 - Genomics
When both parents have a sickle cell trait, what is the chance that a child will have sickle cell disease?
25% RATIONALE: Sickle cell is an autosomal recessive genetic disorder. If both individuals have sickle cell traits, there is a 25% chance they will produce a child with the disease. Children will have a 50% chance of having sickle cell trait. A 75% chance of having offspring sickle cell trait or disease is not mathematically possibly. A child born of parents who both have sickle cell disease will have 100% chance of having the disease
Which assessment finding in a newborn is suggestive of cystic fibrosis?
Abdominal distention RATIONALE: Meconium ileus is an indication that a newborn may have cystic fibrosis. The small intestine is blocked with thick, tenacious, mucilaginous meconium, usually near the ileocecal valve. This causes intestinal obstruction with abdominal distention, vomiting, and fluid electrolyte imbalance. Rapid heart rate is not a sign of cystic fibrosis in the newborn. Excessive crying does not have a special significance in cystic fibrosis. Sternal retractions are not a sign of cystic fibrosis in the newborn.
The couple in the fertility clinic has learned that one of them carries a gene for a serious condition and that the other parent does not carry the gene. They have been told that there is a 50% chance that their child will have this condition. Which pattern of genetic inheritance is this?
Autosomal dominant RATIONALE: An autosomal dominant disorder is caused by 1 defective dominant gene passed to an offspring by a parent with the gene and the disorder. An X-linked recessive disorder usually occurs in males; it is not an autosomal disorder. In an autosomal recessive inheritance pattern, both parents must carry the gene for the offspring to be affected. With an autosomal recessive pattern there is a 25% chance of each child having the genetic condition if both parents carry the gene. A chromosomal disorder relates to a defective chromosome, not a defective gene.
Which genetic pattern describes an autosomal recessive pattern of inheritance?
Both parents are carriers of cystic fibrosis RATIONALE: One recessive gene must be inherited from each parent for the trait to be expressed. The child who inherits one recessive gene will be a carrier. There is no probability of reproduction if parents have the disorder, because the male is infertile. Infertility is a result of the effect on the mucus-secreting glands of the genital tract. The child may be a carrier or not have the gene if one parent is a carrier
The nurse is discussing the need for genetic counseling with a teenager who has a sibling with cystic fibrosis (CF). The identification of which test by the teenager indicates that they understand the genetic counseling?
Carrier testing RATIONALE: More than one gene can cause cystic fibrosis (CF); carrier testing is done to detect known alleles. The results of a chest x-ray will not determine whether the individual is a carrier of CF; this may be one of the tests that are conducted when CF is suspected. A sweat chloride test is performed to diagnose CF, not to determine whether the adolescent is a carrier. CF does not result from a chromosomal anomaly.
Which pathophysiologic abnormality is present in cystic fibrosis?
Dysfunction of mucus-secreting glands RATIONALE: Cystic fibrosis is a genetic disorder affecting all mucus-secreting (exocrine) glands. A sweat gland abnormality is not involved in cystic fibrosis; children with cystic fibrosis lose excessive amounts of sodium through perspiration caused by exocrine gland dysfunction. Cilia action may be influenced by the thickened secretions, but the cilia are not affected by cystic fibrosis. Exocrine, not endocrine, glands are involved in cystic fibrosis.
The parent of an infant with Down syndrome asks the cause. Before responding, the nurse recalls that the genetic factor of Down syndrome results from which finding?
Extra chromosomal material RATIONALE: Down Syndrome (trisomy 21) results from extra chromosomal material on chromosome 21. Down syndrome does not result from a maternal infection. Down syndrome is not related to an X-linked or Y-linked gene. An autosomal recessive gene is not the cause of Down syndrome, although translocation of chromosomes 15 and 21 or 22 is a genetic aberration found in some children with Down syndrome.
The nurse is instructing a community group regarding risk factors for coronary artery disease. Which risk factor cannot be modified?
Heredity RATIONALE: Heredity refers to genetic makeup and cannot be changed. Cigarette smoking is a lifestyle habit that involves behavior modification. Hypertension and diabetes mellitus are risk factors of coronary artery disease that can be controlled with diet, medication, and exercise
A male adolescent with cystic fibrosis, whose parents are both carriers of the disease, asks the nurse, 'When I have children, could they have cystic fibrosis like me?' Which information would the nurse consider before responding?
Men with cystic fibrosis usually are sterile, although sexual function is not affected. RATIONALE: Because of inadequate development of the vas deferens, epididymis, seminal vesicles, and blockage of the vas deferent with thickened secretions, the production of sperm is diminished or absent in males with cystic fibrosis, and most men with the disease are sterile. Cystic fibrosis is inherited as an autosomal recessive trait; it is not sex linked.
Which complication of cystic fibrosis is related to frequent stools and tenacious mucus?
Rectal prolapse RATIONALE: Rectal prolapse, a common gastrointestinal complication of cystic fibrosis, results from the wasting of perirectal supporting tissues because of malnutrition. Anal fissures usually do not occur with cystic fibrosis. Intussusception is not associated with cystic fibrosis. Meconium ileus is associated with cystic fibrosis in newborn; it prevents the passage of meconium.
The nurse anticipates that a child born with a missing chromosome is most likely to have which condition?
Turner Syndrome RATIONALE: Turner syndrome results from a missing X chromosome; these females have an XO configuration rather than XX. Cretinism occurs in the presence of thyroid hormone deficiency. Phenylketonuria is an autosomal recessive single-gene disorder. Down syndrome results from extra genetic material on chromosome 21
Which assessment would the nurse recognize as common in infants with Down syndrome?
Abnormal heart sounds RATIONALE: Cardiac anomalies (that produce abnormal heart sounds) often accompanying genetic problems such as Down syndrome; 30% to 40% of affected infants also have congenital heart defects. Infants with Down syndrome do not have increased intracranial pressure; the fontanels should be flat. The extremities will more likely be relaxed. Children with Down syndrome exhibit the usual pupillary reaction to light.
A 26-year-old woman whose sister recently had a lumpectomy for breast cancer calls the local women's health center and asks for an appointment for a mammogram. Which guidance would the nurse provide the client?
An appointment should be given for history, assessment, and indicated imaging. RATIONALE: The client would be advised to have an appointment that ideally would include detailed family history including any genetic testing that may have been done on the client's sister, examination, and counseling regarding her options in genetic testing and imaging as indicated. The American Cancer Society (ACS), The American College of Obstetricians and Gynecologists (ACOG), and the United States Preventative Task Force (USPTF) all have different recommendations for breast cancer screening. The approach of shared decision-making is advocated, which is where the known information is presented the client and she shares in the decision-making regarding screening for breast cancer. It would be incorrect to say that genetic testing is required. Genetic testing is always involuntary, and the client may decline after being counseled. An MRI scan is an option for women at higher risk of breast cancer, but it is generally used in conjunction with another imaging mode such as a mammogram.
The nurse is caring for a school-aged child with cystic fibrosis. Which pathophysiologic factor has the greatest effect on the child's health status?
Extremely thick mucus causing obstructed airways RATIONALE: Dysfunction of the exocrine glands leads to an excessive accumulation of thick mucus, a slower flow rate of mucus, and incomplete expectoration of mucus, all of which contribute to airway obstruction. Acute inflammation of the lung parenchyma is associated with pneumonia, not cystic fibrosis. The endocrine glands are not affected in cystic fibrosis. Increased irritability of the airways that causes obstruction is associated with asthma, not cystic fibrosis.
The parent of a child with sickle cell anemia (SCA) tell the nurse, "We have never had any symptoms of SCA and do not understand why our child has this problem." Which information will the nurse include when teaching the parents?
If both parents are carriers of SCA, there is a 25% chance that offspring will have SCA. RATIONALE: People who have 1 gene for SCA are described as having sickle cell trait or as carriers of SCA and are usually asymptomatic for sickling-related complications. Sickle cell anemia is not random; the gene must come from both parents. If both parents are carriers, with each pregnancy there is a 25% chance that the child may have the disease and a 50% chance that the child will be a carrier. Genetic testing is not needed to establish the presence of sickle cell trait when two asymptomatic parents have a child with SCA because SCA is an autosomal recessive inherited condition and both parents must be carriers to have a child with SCA.
Which pathophysiological process would the nurse expect to account for growth failure in a 4-year-old child with newly diagnosed cystic fibrosis?
Impaired digestion and absorption because of lack of pancreatic enzymes RATIONALE: Obstruction of the pancreatic duct and the absence of enzymes (e.g., trypsin, amylase, lipase) to aid fat digestion and absorption lead to wasting of tissues and failure to thrive. Currently it is recommended that children with cystic fibrosis consume 150% to 200% of the calories recommended for their body weight. Despite dyspnea and shortness of breath, these children have voracious appetites when feeling well; the difficulty involves poor digestion and malabsorption of fats and fat-soluble vitamins. Increased bowel motility and diarrhea are not associated with cystic fibrosis. The pulmonary disease process leads to localized respiratory dysfunction, not to retard physical growth.
Which common concern of most parents of children with sickle cell anemia would the nurse address at a family education conference?
Sharing feelings regarding the transmission of the disorder RATIONALE: Discussion with parents who have children with similar problems help ease their discomfort and feelings of guilt. This is especially true in regard to genetically transmitted diseases. Children with sickle cell anemia should be allowed to attend the same schools as their healthy peers. There is no recommended therapeutic climate for children with sickle cell anemia. Some parents do not choose to avoid future pregnancies, and they should not be encouraged to do so.
Which education would the nurse provide to the family of a 10-year-old child diagnosed with hemophilia about the genetic inheritance of the condition?
The mother is a carrier of the disorder but usually is not affected by it. RATIONALE: The hemophilia gene is carried on the X chromosome but is recessive. The female is the carrier (an unaffected XO and an affected XH). If the male receives the affected XH(XHYO), they will have the disorder. Hemophilia is carried by the female; the Mendelian laws of inheritance are not sex specific. Hemophilia is a sex-linked recessive disorder. Only females carry the trait; usually males are affected.
The nurse genetic counselor is working with a couple, each of whom is a carrier of an autosomal-recessive disorder. Which statement indicates that the couple has understood the teaching about this disorder?
There is a 1-in-4 chance of having a child with the disorder RATIONALE: According to Mendelian genetic theory, when both parents are carriers of an autosomal-recessive disorder there is a 1-in-4 chance or 25% probability that a child will have the disorder. The statement that none of the children will have the disorder indicates that the couple does not understand Mendel's theory of probability. When both parents are carriers, there is a 1-in-2 chance or 50% probability that a child will be a carrier and a 1-in-4 chance or 25% probability that a child will have the disorder. If one of the parents has the disorder, there is a 1-in-2 chance or 50% probability that a child will have the disorder.
A healthy couple whose child has cystic fibrosis (CF) is concerned about having another child with the disease. Knowing that this disorder has an autosomal-recessive mode of inheritance, how would the nurse respond?
There is a 25% chance the baby will be affected and a 50% chance that the baby will be a carrier. RATIONALE: According to Mendelian law, because both parents are carriers, this baby has a 50% chance of being a carrier, a 25% chance of having the disease, and a 25% chance of being unaffected. Because this is an autosomal-recessive gene and not X-linked, there is not difference in prevalence between male and female genetic distribution. Regardless of sex, the infant will have the same risk of being a carrier or noncarrier or having the expressive trait for CF
