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Which genetic term refers to a person who possesses one copy of an affected gene and one copy of an unaffected gene and is clinically unaffected?
- A. Allele
- B. Carrier
- C. Pedigree
- D. Multifactorial
Correct Answer: B
Rationale: An individual who is a carrier is asymptomatic but possesses a genetic alteration, either in the form of a gene or chromosome change. Alleles are alternative expressions of genes at a different locus. A pedigree is a diagram that describes family relationships, gender, disease, status, or other relevant information about a family. Multifactorial describes a complex interaction of both genetic and environmental factors that produce an effect on the individual.
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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.
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.
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.
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 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.