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The nurse is counselling a couple in which the man has an autosomal recessive disorder, and the woman has no gene for the disorder. The nurse uses Punnett squares to show the couple that the probability of their having a child with the disorder is which of the following percentages?
- A. 0%
- B. 25%
- C. 50%
- D. 75%
Correct Answer: A
Rationale: When one parent has no gene for an autosomal recessive disorder, the children will not display the characteristics of the disorder. However, the children will be carriers of the autosomal recessive disorder.
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The parents of a child with cystic fibrosis ask if their next child will also be affected. Which of the following is the basis for the nurse's response related to autosomal recessive disorders?
- A. There is a 25% chance that the child will be affected.
- B. All male offspring are affected.
- C. There is a 50% chance that the child will be affected.
- D. All female offspring will be affected.
Correct Answer: A
Rationale: Cystic fibrosis is an autosomal recessive disorder, meaning that there is a 25% chance that offspring will be affected. It happens equally in males and females.
A newly pregnant woman asks the nurse what the best time is for a prenatal diagnostic amniocentesis? Which of the following time frames is the basis for the nurses' response?
- A. 7-10 weeks
- B. 11-13 weeks
- C. 15-17 weeks
- D. 20-24 weeks
Correct Answer: C
Rationale: A prenatal diagnostic ultrasound should be done between 15 and 17 weeks of gestation during which amniocentesis can be performed.
A male with mild hemophilia asks the nurse, 'Will my children have hemophilia?' Which of the following responses by the nurse is most appropriate?
- A. All of your children will be at risk for hemophilia.
- B. Hemophilia is a multifactorial inherited condition.
- C. Only your male children are at risk for hemophilia.
- D. Your female children will be carriers for hemophilia.
Correct Answer: D
Rationale: Because hemophilia is caused by a mutation of the X-chromosome, all female children of a man with hemophilia are carriers of the disorder and can transmit the mutated gene to their offspring. Sons of a man with hemophilia will not have the disorder. Hemophilia is caused by a genetic mutation and is not a multifactorial inherited condition.
A pregnant patient with a family history of cystic fibrosis (CF) asks the emergency department nurse for information about genetic testing. Which of the following actions is most appropriate for the nurse to take?
- A. Refer the patient to a qualified genetic counsellor.
- B. Ask the patient why genetic testing is important to her.
- C. Remind the patient that genetic testing has many social implications.
- D. Tell the patient that cystic fibrosis is an autosomal-recessive disorder.
Correct Answer: A
Rationale: Although the nurse should understand basic genetics, the emergency department is often not the ideal environment for genetic counselling. A genetic nurse or counsellor is best qualified to address the multiple issues involved in genetic testing for a patient who is considering having children. Although genetic testing does have social implications, a pregnant patient will be better served by a genetic counsellor who will have more expertise in this area. CF is an autosomal-recessive disorder, but the patient might not understand the implications of this statement. Asking why the patient feels genetic testing is important may imply to the patient that the nurse is questioning her value system regarding issues such as abortion.
When taking a family history in the genetic clinic, the nurse will ask information about how many generations in the past?
- A. 2
- B. 3
- C. 4
- D. 5
Correct Answer: B
Rationale: A detailed three-generation family history, or pedigree, offers great insight into possible genetic conditions within a family.