Nokea
The nurse is teaching parents of a child with cri du chat syndrome about this disorder. The nurse understands parents understand the teaching if they make which statement?
- A. This disorder is very common.
- B. This is an autosomal recessive disorder.
- C. The crying pattern is abnormal and catlike.
- D. The child will always have a moon-shaped face.
Correct Answer: C
Rationale: Typical of this disease is a crying pattern that is abnormal and catlike. Cri du chat, or cats cry, syndrome is a rare (one in 50,000 live births) chromosome deletion syndrome, not autosomal recessive, resulting from loss of the small arm of chromosome 5. In early infancy this syndrome manifests with a typical but nondistinctive facial appearance, often a moon-shaped face with wide-spaced eyes (hypertelorism). As the child grows, this feature is progressively diluted, and by age 2 years, the child is indistinguishable from age-matched control participants.
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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.
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.
Which is a birth defect or disorder that occurs as a new case in a family and is not inherited?
- A. Sporadic
- B. Polygenic
- C. Monosomy
- D. Association
Correct Answer: A
Rationale: Sporadic describes a birth defect previously unidentified in a family. It is not inherited. Polygenic inheritance involves the inheritance of many genes at separate loci whose combined effects produce a given phenotype. Monosomy is an abnormal number of chromosomes whereby the chromosome is represented by a single copy in a somatic cell. A nonrandom cluster of malformations without a specific cause is an association.
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.
Turner syndrome is suspected in an adolescent girl with short stature. What causes this?
- A. Absence of one of the X chromosomes
- B. Presence of an incomplete Y chromosome
- C. Precocious puberty in an otherwise healthy child
- D. Excess production of both androgens and estrogens
Correct Answer: A
Rationale: Turner syndrome is caused by an absence of one of the X chromosomes. Most girls who have this disorder have one X chromosome missing from all cells. No Y chromosome is present in individuals with Turner syndrome. These young women have 45 rather than 46 chromosomes.