While talking with a pregnant woman who has undergone genetic testing, the woman informs the nurse that her baby will be born with Down syndrome. The nurse understands that Down syndrome is an example of:
Trisomy numeric abnormality
Multifactorial inheritance
X-linked recessive inheritance
Chromosomal deletion
The Correct Answer is A
Choice A Reason: Trisomy numeric abnormality. Down syndrome is a genetic disorder that occurs when a person has three copies of chromosome 21 instead of two. This extra chromosome causes various physical and mental features that vary from person to person. Down syndrome is also called trisomy 21 because it involves three copies of chromosome 21.
Choice B Reason: Multifactorial inheritance is incorrect because it refers to a type of genetic disorder that results from the interaction of multiple genes and environmental factors. Examples of multifactorial disorders include cleft lip or palate, neural tube defects, diabetes, hypertension, and some types of cancer.
Choice C Reason: X-linked recessive inheritance is incorrect because it refers to a type of genetic disorder that affects males more than females because it is caused by a mutation on the X chromosome. Females have two X chromosomes, so they can be carriers or affected depending on whether they inherit one or two copies of the mutated gene. Males have one X chromosome and one Y chromosome, so they are always affected if they inherit the mutated gene from their mother. Examples of X-linked recessive disorders include hemophilia, color blindness, and Duchenne muscular dystrophy.
Choice D Reason: Chromosomal deletion is incorrect because it refers to a type of genetic disorder that occurs when a part of a chromosome is missing or deleted. This can cause various physical and mental problems depending on the size and location of the deletion. Examples of chromosomal deletion
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
Choice A Reason: This is incorrect because sickle-cell anemia is a genetic disorder that affects the shape and function of red blood cells. It does not affect the AFP level, which is a protein produced by the fetus and placenta. Sickle-cell anemia can be detected by other prenatal tests, such as hemoglobin electrophoresis or DNA analysis.
Choice B Reason: This is incorrect because cardiac defects are structural abnormalities of the heart or blood vessels that affect the blood flow and oxygen delivery to the fetus. They may cause an increased AFP level, not a decreased one, as they can lead to fetal distress or edema. Cardiac defects can be detected by other prenatal tests, such as fetal echocardiography or ultrasound.
Choice C Reason: This is correct because Down syndrome is a chromosomal disorder that results from an extra copy of chromosome 21. It causes various physical and mental developmental delays and defects in the fetus. It is associated with a decreased AFP level, as well as decreased levels of human chorionic gonadotropin (hCG) and unconjugated estriol (uE3). Down syndrome can be confirmed by other prenatal tests, such as amniocentesis or chorionic villus sampling (CVS).
Choice D Reason: This is incorrect because respiratory disorders are problems that affect the breathing and gas exchange of the fetus. They may cause an increased AFP level, not a decreased one, as they can lead to fetal distress or edema. Respiratory disorders can be detected by other prenatal tests, such as fetal biophysical profile (BPP) or nonstress test (NST).
Correct Answer is D
Explanation
Choice A: 28 weeks' gestation is too early to screen for group B streptococcus infection. Group B streptococcus (GBS) is a type of bacteria that can cause serious infections in newborns if transmitted from the mother during labor and delivery. The optimal time to screen for GBS is between 35 and 37 weeks' gestation.
Choice B: 32 weeks' gestation is also too early to screen for GBS infection. Screening at this time may not reflect the true colonization status of the mother at the time of delivery, as GBS can be transient or intermittent.
Choice C: 16 weeks' gestation is much too early to screen for GBS infection. Screening at this time has no clinical value, as GBS colonization can change throughout pregnancy.
Choice D: 36 weeks' gestation is the appropriate time to screen for GBS infection. Screening at this time can identify mothers who are colonized with GBS and who need intrapartum antibiotic prophylaxis to prevent neonatal sepsis, pneumonia, and meningitis.
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