twins that derive from a single zygote that has split into two are called
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HESI Maternity 55 Questions

1. Twins that derive from a single zygote that has split into two are called:

Correct answer: A

Rationale: The correct answer is A: monozygotic (MZ) twins. Monozygotic twins, also known as identical twins, occur when a single zygote splits into two embryos, leading to two genetically identical individuals. Choice B, fraternal twins, are twins that develop from two separate eggs fertilized by two different sperm cells, resulting in non-identical siblings. Choice C, non-identical twins, is not a common term used to describe this type of twinning. Choice D, dizygotic (DZ) twins, refer to twins that develop from two separate eggs fertilized by two different sperm cells, leading to non-identical twins.

2. What is a procedure for using ultrasonic sound waves to create a picture of an embryo or fetus?

Correct answer: B

Rationale: A sonogram, also known as an ultrasound, is a procedure that utilizes sound waves to generate images of a developing embryo or fetus. This imaging technique is commonly used in prenatal care to monitor fetal development and identify any potential abnormalities. Choices A, C, and D are incorrect because a phenotype refers to an individual's observable traits resulting from genetic and environmental influences, a genotype is an individual's genetic makeup, and an alpha-fetoprotein (AFP) assay is a blood test used to screen for certain birth defects.

3. Monozygotic (MZ) twins are known as fraternal twins.

Correct answer: B

Rationale: The correct answer is B: 'FALSE.' Monozygotic (MZ) twins are identical twins, not fraternal. Fraternal twins are dizygotic (DZ). The statement in the question is incorrect as MZ twins are genetically identical, while fraternal twins actually refer to dizygotic twins who develop from two separate fertilized eggs. Therefore, monozygotic twins are not known as fraternal twins, making option B the correct choice. Options A, C, and D are incorrect as they do not accurately describe the relationship between monozygotic and fraternal twins.

4. What causes sickle-cell anemia?

Correct answer: C

Rationale: Sickle-cell anemia is a genetic disorder caused by inheriting two copies of a recessive gene, one from each parent. The correct answer is C. Choice A is incorrect because sickle-cell anemia is not primarily caused by a chromosomal abnormality. Choice B is incorrect as the condition is not linked to a single segment found only on the Y chromosome. Choice D is unrelated as it mentions a decrease in estrogen levels, which is not a cause of sickle-cell anemia.

5. A client who is receiving prenatal care is at her 24-week appointment. Which of the following laboratory tests should the nurse plan to conduct?

Correct answer: B

Rationale: The correct answer is B: 1-hour glucose tolerance test. At around 24-28 weeks of gestation, a pregnant individual is typically screened for gestational diabetes. The 1-hour glucose tolerance test helps in identifying elevated blood sugar levels during pregnancy. Choice A, Group B strep culture, is not typically performed at the 24-week appointment but later in the third trimester to screen for Group B streptococcus colonization. Choice C, Rubella titer, is usually checked early in pregnancy to determine immunity to rubella. Choice D, Blood type and Rh, is important for determining the client's blood type and Rh status, but it is usually done earlier in pregnancy and not specifically at the 24-week appointment.

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