Nokea
A woman, age 43 years, is 6 weeks pregnant. It is important that she be informed of which?
- A. The need for a therapeutic abortion
- B. Increased risk for Down syndrome
- C. Increased risk for Turner syndrome
- D. The need for an immediate amniocentesis
Correct Answer: B
Rationale: Women who are older than age 35 years at the birth of a single child or 31 years at the birth of twins are advised to have prenatal diagnosis. The risk of having a child with Down syndrome increases with maternal age. There is no indication of a need for a therapeutic abortion at this stage. Turner syndrome is not associated with advanced maternal age. Amniocentesis cannot be done at a gestational age of 6 weeks.
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Which is characteristic of X-linked recessive inheritance?
- A. There are no carriers.
- B. Affected individuals are principally males.
- C. Affected individuals are principally females.
- D. Affected individuals will always have affected parents.
Correct Answer: B
Rationale: In X-linked recessive disorders, the affected individuals are usually male. With recessive traits, usually two copies of the gene are needed to produce the effect. Because the male only has one X chromosome, the effect is visible with only one copy of the gene. Females are usually only carriers of X-linked recessive disorders. The X chromosome that does not have the recessive gene will produce the normal protein, so the woman will not show evidence of the disorder. The transmission is from mother to son. Usually the mother and father are unaffected.
The inheritance of which is X-linked recessive?
- A. Hemophilia A
- B. Marfan syndrome
- C. Neurofibromatosis
- D. Fragile X syndrome
Correct Answer: A
Rationale: Hemophilia A is inherited as an X-linked recessive trait. Marfan syndrome and neurofibromatosis are inherited as autosomal dominant disorders. Fragile X is inherited as an X-linked trait.
The nurse is assessing a neonate who was born 1 hour ago to healthy white parents in their early forties. Which finding should be most suggestive of Down syndrome?
- A. Hypertonia
- B. Low-set ears
- C. Micrognathia
- D. Long, thin fingers and toes
Correct Answer: B
Rationale: Children with Down syndrome have low-set ears. Infants with Down syndrome have hypotonia, not hypertonia. Micrognathia is common in trisomy 16, not Down syndrome. Children with Down syndrome have short hands with broad fingers.
Which abnormality is a common sex chromosome defect?
- A. Down syndrome
- B. Turner syndrome
- C. Marfan syndrome
- D. Hemophilia
Correct Answer: B
Rationale: Turner syndrome is caused by an absence of one of the X chromosomes. Down syndrome is caused by trisomy 21 (three copies rather than two copies of chromosome 21). Marfan syndrome is a connective tissue disorder inherited in an autosomal dominant pattern. Hemophilia is a disorder of blood coagulation inherited in an X-linked recessive pattern.
A father with an X-linked recessive disorder asks the nurse what the probability is that his sons will have the disorder. Which response should the nurse make?
- A. Male children will be carriers.
- B. All male children will be affected.
- C. None of the sons will have the disorder.
- D. It cannot be determined without more data.
Correct Answer: C
Rationale: When a male has an X-linked recessive disorder, he has one copy of the allele on his X chromosome. The father passes only his Y chromosome (not the X chromosome) to his sons. Therefore, none of his sons will have the X-linked recessive gene. They will not be carriers or be affected by the disorder. No additional data are needed to answer this question.