monozygotic mz twins are known as fraternal twins
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Maternity HESI Practice Questions

1. 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.

2. Dizygotic (DZ) twins share _________ percent of their genes.

Correct answer: C

Rationale: Dizygotic (DZ) twins share approximately 50% of their genes. This is because dizygotic twins, also known as fraternal twins, originate from two separate fertilized eggs and share similar genetic similarity to regular siblings. Choice A (100%) is incorrect because if twins shared 100% of their genes, they would be identical twins (monozygotic). Choice B (75%) is incorrect as it is not the typical genetic similarity seen in dizygotic twins. Choice D (25%) is incorrect as it represents a significantly lower genetic similarity than what is observed in dizygotic twins.

3. Which of the following statements is true of sickle-cell anemia?

Correct answer: C

Rationale: The correct answer is C. Sickle-cell anemia results from a mutation in the beta-globin gene, causing red blood cells to become sickle-shaped. These misshapen cells can obstruct small blood vessels, leading to reduced oxygen delivery to tissues. Choices A, B, and D are incorrect because sickle-cell anemia is typically managed with treatments such as pain relief medications, hydration, and in severe cases, blood transfusions. It is caused by a specific mutation in the beta-globin gene, not by the inability to metabolize phenylalanine. Additionally, sickle-cell anemia is more prevalent in individuals of African, Mediterranean, Middle Eastern, and Indian descent, not exclusive to any specific gender.

4. A newborn's head circumference is 12 inches (30.5 cm) and his chest measurement is 13 inches (33 cm). The nurse notes that this infant has no molding, and it was a breech presentation delivered by cesarean section. What action should the nurse take based on this data?

Correct answer: D

Rationale: Head and chest circumference measurements are within normal limits for a newborn, especially for those delivered by cesarean section, so no immediate action is required beyond documentation.

5. Once the testes have developed in the embryo, they begin to produce male sex hormones, or _____.

Correct answer: A

Rationale: Androgens are male sex hormones, such as testosterone, produced by the testes after they have developed in the embryo. Androgens are responsible for the development of male secondary sexual characteristics. Genotypes refer to an individual's genetic makeup, not hormones. Blastocysts are early stage embryos, not male sex hormones. Teratogens are substances that can interfere with fetal development, not male sex hormones produced by the testes.

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