Nokea
Parents ask the nurse about the characteristics of autosomal dominant inheritance. Which statement is characteristic of autosomal dominant inheritance?
- A. Females are affected with greater frequency than males.
- B. Unaffected children of affected individuals will have affected children.
- C. Each child of a heterozygous affected parent has a 50% chance of being affected.
- D. Any child of two unaffected heterozygous parents has a 25% chance of being affected.
Correct Answer: C
Rationale: In autosomal dominant inheritance, only one copy of the mutant gene is necessary to cause the disorder. When a parent is affected, there is a 50% chance that the chromosome with the gene for the disorder will be contributed to each pregnancy. Males and females are equally affected. The disorder does not skip a generation. If the child is not affected, then most likely he or she is not a carrier of the gene for the disorder. In autosomal recessive inheritance, any child of two unaffected heterozygous parents has a 25% chance of being affected.
You may also like to solve these questions
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).
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 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.
Chromosome analysis of the fetus is usually accomplished through the testing of which?
- A. Fetal serum
- B. Maternal urine
- C. Amniotic fluid
- D. Maternal serum
Correct Answer: C
Rationale: Amniocentesis is the most common method to retrieve fetal cells for chromosome analysis. Viable fetal cells are sloughed off into the amniotic fluid, and when a sample is taken, they can be cultured and analyzed. It is difficult to obtain a sample of the fetal blood. It is a high-risk situation for the fetus. Fetal cells are not present in the maternal urine or blood.