Chapter 3: Hereditary Influences on Health Promotion of the Child and Family

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.

ANS: A 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 inheritance of which is X-linked recessive? a. Hemophilia A b. Marfan syndrome c. Neurofibromatosis d. Fragile X syndrome

ANS: A 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.

Parents ask the nurse about the characteristics of autosomal recessive inheritance. Which is characteristic of autosomal recessive inheritance? a. Affected individuals have unaffected parents. b. Affected individuals have one affected parent. c. Affected parents have a 50% chance of having an affected child. d. Affected parents will have unaffected children.

ANS: A Parents who are carriers of a recessive gene are asymptomatic. For a child to be affected, both parents must have a copy of the gene, which is passed to the child. Both parents are asymptomatic but can have affected children. In autosomal recessive inheritance, there is a 25% chance that each pregnancy will result in an affected child. In autosomal dominant inheritance, affected parents can have unaffected children.

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

ANS: A 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.

A couple expecting their first child has a positive family history for several congenital defects and disorders. The couple tells the nurse that they are opposed to abortion for religious reasons. Which should the nurse consider when counseling the couple? a. The couple should be encouraged to have recommended diagnostic testing. b. The couple needs counseling regarding advantages and disadvantages of pregnancy termination. c. Diagnostic testing is required by law in this situation. d. Diagnostic testing is of limited value if termination of pregnancy is not an option.

ANS: A The benefits of prenatal diagnostic testing extend beyond decisions concerning abortion. If the child has congenital disorders, decisions can be made about fetal surgery if indicated. In addition, if the child is expected to require neonatal intensive care at birth, the mother is encouraged to deliver at a level III neonatal center. The couple is counseled about the advantages and disadvantages of prenatal diagnosis, not pregnancy termination, although the family cannot be forced to have prenatal testing. The information gives the parents time to grieve and plan for their child if congenital disorders are present. If the child is free of defects, then the parents are relieved of a major worry.

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

ANS: A 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.

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

ANS: B 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.

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

ANS: B 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 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.

ANS: B 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.

Which abnormality is a common sex chromosome defect? a. Down syndrome b. Turner syndrome c. Marfan syndrome d. Hemophilia

ANS: B 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 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

ANS: B 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.

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

ANS: C 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

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.

ANS: C 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 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

ANS: C 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 genetic term refers to the transfer of all or part of a chromosome to a different chromosome after chromosome breakage? a. Trisomy b. Monosomy c. Translocation d. Nondisjunction

ANS: C Translocation is the transfer of all or part of a chromosome to a different chromosome after chromosome breakage. It can be balanced, producing no phenotypic effects, or unbalanced, producing severe or lethal effects. Trisomy is an abnormal number of chromosomes caused by the presence of an extra chromosome, which is added to a given chromosome pair and results in a total of 47 chromosomes per cell. Monosomy is an abnormal number of chromosomes whereby the chromosome is represented by a single copy in a somatic cell. Nondisjunction is the failure of homologous chromosomes or chromatids to separate during mitosis or meiosis.

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."

ANS: C Typical of this disease is a crying pattern that is abnormal and catlike. Cri du chat, or cat's 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.

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."

ANS: C 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.

Parents ask the nurse if there was something that should have been done during the pregnancy to prevent their child's cleft lip. Which statement should the nurse give as a response? a. "This is a type of deformation and can sometimes be prevented." b. "Studies show that taking folic acid during pregnancy can prevent this defect." c. "This is a genetic disorder and has a 25% chance of happening with each pregnancy." d. "The malformation occurs at approximately 5 weeks of gestation; there is no known way to prevent this."

ANS: D Cleft lip, an example of a malformation, occurs at approximately 5 weeks of gestation when the developing embryo naturally has two clefts in the area. There is no known way to prevent this defect. Deformations are often caused by extrinsic mechanical forces on normally developing tissue. Club foot is an example of a deformation often caused by uterine constraint. Cleft lip is not a genetic disorder; the reasons for this occurring are still unknown. Taking folic acid during pregnancy can help to prevent neural tube disorders but not cleft lip defects.

A couple asks the nurse about the optimal time for genetic counseling. They do not plan to have children for several years. When should the nurse recommend they begin genetic counseling? a. As soon as the woman suspects that she may be pregnant b. Whenever they are ready to start their family c. Now, if one of them has a family history of congenital heart disease d. Now, if they are members of a population at risk for certain diseases

ANS: D Persons who seek genetic evaluation and counseling must first be aware if there is a genetic or potential problem in their families. Genetic testing should be done now if the couple is part of a population at risk. It is not feasible at this time to test for all genetic diseases. The optimal time for genetic counseling is before pregnancy occurs. During the pregnancy, genetic counseling may be indicated if a genetic disorder is suspected. Congenital heart disease is not a single-gene disorder.

The nurse is reviewing a client's 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)

ANS: D 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.