Conception, Fetal Growth, Genetics

A key finding from the Human Genome Project is: A approximately 20,000 to 25,000 genes make up the genome. B all human beings are 80.99% identical at the DNA level. C human genes produce only one protein per gene; other mammals produce three proteins per gene. D single-gene testing will become a standardized test for all pregnant women in the future.

A Approximately 20,500 genes make up the human genome; this is only twice as many as make up the genomes of roundworms and flies. Human beings are 99.9% identical at the DNA level. Most human genes produce at least three proteins. Single-gene testing (e.g., alpha-fetoprotein) is already standardized for prenatal care.

Most of the genetic tests now offered in clinical practice are tests for: A single-gene disorders. B carrier screening. C predictive values. D predispositional testing.

A Most tests now offered are tests for single-gene disorders in clients with clinical symptoms or who have a family history of a genetic disease. Carrier screening is used to identify individuals who have a gene mutation for a genetic condition but do not display symptoms. Predictive testing is used only to clarify the genetic status of asymptomatic family members. Predispositional testing differs from the other types of genetic screening in that a positive result does not indicate a 100% chance of developing the condition.

The nurse should teach a pregnant woman that which substances are teratogens? (Select all that apply) A Cigarette smoke Correct B Isotretinoin (Retin A) C Vitamin C D Salicylic acid E Rubella

A, B, E Rationale: Vitamin C and salicylic acid are not known teratogens.

What best describes the pattern of genetic transmission known as autosomal recessive inheritance? A Disorders in which the abnormal gene for the trait is expressed even when the other member of the pair is normal B Disorders in which both genes of a pair must be abnormal for the disorder to be expressed C Disorders in which a single gene controls the particular trait D Disorders in which the abnormal gene is carried on the X chromosome

B Autosomal dominant inheritance occurs when the abnormal gene for the trait is expressed, even when the other member of the pair is normal, such as Huntington disease or Marfan syndrome. An autosomal recessive inheritance disorder occurs when both genes of the pair are abnormal, such as phenylketonuria or sickle cell anemia. Disorders in which a single gene controls the particular trait describe the unifactorial inheritance. X-linked recessive inheritance occurs when the abnormal gene is carried on the X chromosome, such as hemophilia or Duchenne muscular dystrophy.

With regard to abnormalities of chromosomes, nurses should be aware that: A they occur in approximately 10% of newborns. B abnormalities of number are the leading cause of pregnancy loss. C down syndrome is a result of an abnormal chromosomal structure. D unbalanced translocation results in a mild abnormality that the child will outgrow.

B Chromosomal abnormalities occur in less than 1% of newborns. Aneuploidy is an abnormality of number that also is the leading genetic cause of mental retardation. Down syndrome is the most common form of trisomal abnormality, an abnormality of chromosome number (47 chromosomes). Unbalanced translocation is an abnormality of chromosome structure that often has serious clinical effects.

A nurse is providing genetic counseling for an expectant couple who already have a child with trisomy 18. The nurse should: A tell the couple they need to have an abortion within 2 to 3 weeks. B explain that the fetus has a 50% chance of having the disorder. C discuss options with the couple, including amniocentesis to determine whether the fetus is affected. D refer the couple to a psychologist for emotional support.

C The couple should be given information about the likelihood of having another baby with this disorder so that they can make an informed decision. A genetic counselor is the best source for determining genetic probability ratios. Genetic testing, including amniocentesis, would need to be performed to determine whether the fetus is affected. The couple eventually may need emotional support, but the status of the pregnancy must be determined first.

A couple has been counseled for genetic anomalies. They ask you, "What is karyotyping?" Your best response is: A "Karyotyping will reveal if the baby's lungs are mature." B "Karyotyping will reveal if your baby will develop normally." C "Karyotyping will provide information about the gender of the baby, and the number and structure of the chromosomes." D "Karyotyping will detect any physical deformities the baby has."

C The lecithin/sphingomyelin ratio, not karyotyping, reveals lung maturity. Although karyotyping can detect genetic anomalies, the range of normal is nondescriptive. Karyotyping provides genetic information, such as gender and chromosomal structure. Although karyotyping can detect genetic anomalies, not all such anomalies display obvious physical deformities. The term deformities is a nondescriptive word. Furthermore, physical anomalies may be present that are not detected by genetic studies (e.g., cardiac malformations).

A woman at 35 weeks of gestation has had an amniocentesis. The results reveal that surface-active phospholipids are present in the amniotic fluid. The nurse is aware that this finding indicates: A the fetus is at risk for Down syndrome. B the woman is at high risk for developing preterm labor. C lung maturity. D meconium is present in the amniotic fluid.

C The presence of surface-active phospholipids is not an indication of Down syndrome. This result reveals the fetal lungs are mature and in no way indicates risk for preterm labor. The detection of the presence of pulmonary surfactants, surface-active phospholipids, in amniotic fluid has been used to determine fetal lung maturity, or the ability of the lungs to function after birth. This occurs at approximately 35 weeks of gestation. Meconium should not be present in the amniotic fluid.

A woman's cousin gave birth to an infant with a congenital heart anomaly. The woman asks the nurse when such anomalies occur during development. Which response by the nurse is most accurate? A "We don't really know when such defects occur." B "It depends on what caused the defect." C "They occur between the third and fifth weeks of development." D "They usually occur in the first 2 weeks of development."

C This is an inaccurate statement. Regardless of the cause, the heart is vulnerable during its period of development, the third to fifth weeks. The cardiovascular system is the first organ system to function in the developing human. Blood vessel and blood formation begins in the third week, and the heart is developmentally complete in the fifth week. This is an inaccurate statement.

With regard to the estimation and interpretation of the recurrence of risks for genetic disorders, nurses should be aware that: A with a dominant disorder, the likelihood of the second child also having the condition is 100%. B an autosomal recessive disease carries a one in eight risk of the second child also having the disorder. C disorders involving maternal ingestion of drugs carry a one in four chance of being repeated in the second child. D the risk factor remains the same no matter how many affected children are already in the family.

D In a dominant disorder, the likelihood of recurrence in subsequent children is 50% (one in two). An autosomal recessive disease carries a one in four chance of recurrence. Subsequent children would be at risk only if the mother continued to use drugs; the rate of risk would be difficult to calculate. Each pregnancy is an independent event. The risk factor (e.g., one in two, one in four) remains the same for each child, no matter how many children are born to the family.