Nokea
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.
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The nurse is reviewing a clients prenatal history. Which prescribed medication does the nurse understand is not considered a teratogen and prescribed during pregnancy?
- A. Phenytoin (Dilantin)
- B. Warfarin (Coumadin)
- C. Isotretinoin (Accutane)
- D. Heparin sodium (Heparin)
Correct Answer: D
Rationale: Teratogens, agents that cause birth defects when present in the prenatal environment, account for the majority of adverse intrauterine effects not attributable to genetic factors. Types of teratogens include drugs (phenytoin [Dilantin], warfarin [Coumadin], isotretinoin [Accutane]). Heparin is the anticoagulant used during pregnancy and is not a teratogen. It does not cross the placenta.
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 couple has given birth to their first child, a boy with a recessive disorder. The genetic counselor tells them that the risk of recurrence is one in four. Which statement is a correct interpretation of this information?
- A. The risk factor remains the same for each pregnancy.
- B. The risk factor will change when they have a second child.
- C. Because the parents have one affected child, the next three children should be unaffected.
- D. Because the parents have one affected child, the next child is four times more likely to be affected.
Correct Answer: A
Rationale: Each pregnancy has the same risks for an affected child. Because an odds ratio reflects the risk, this does not change over time. The statement by the genetic counselor refers to a probability. This does not change over time. The statement Because the parents have one affected child, the next child is four times more likely to be affected does not reflect autosomal recessive inheritance.
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 is a sex chromosome abnormality that is caused by the presence of one or more additional X chromosomes in a male?
- A. Turner
- B. Triple X
- C. Klinefelter
- D. Trisomy 13
Correct Answer: C
Rationale: Klinefelter syndrome is characterized by one or more additional X chromosomes. These individuals are tall with male secondary sexual characteristics that may be deficient, and they may be learning disabled. An absence of an X chromosome results in Turner syndrome. Triple X and trisomy 13 are not abnormalities that involve one or more additional X chromosomes in a male (Klinefelter syndrome).