dizygotic dz twins share percent of their genes
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HESI Focus on Maternity Exam

1. 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.

2. _____ is a type of estrogen, prescribed in the 1940s and 1950s to pregnant women, that is said to have caused testicular, vaginal, and cervical cancer in some offspring.

Correct answer: D

Rationale: Diethylstilbestrol (DES) is a synthetic estrogen that was prescribed to pregnant women in the 1940s and 1950s to prevent miscarriages. However, it was later discovered that DES exposure in utero could lead to health issues in offspring, including an increased risk of testicular, vaginal, and cervical cancer. Choice A, Androsterone, is a steroid hormone produced in small amounts in humans and unlikely to be associated with the adverse effects described. Choice B, Adiponectin, is a protein hormone that plays a role in regulating glucose levels and fatty acid breakdown, not related to the adverse effects mentioned. Choice C, Progestin, is a synthetic form of progesterone used in birth control and hormone therapy, not linked to the specific health concerns associated with DES exposure.

3. Twenty-year-old Jack is extremely tall and has very thick facial hair. Most of his male secondary sex characteristics are also more pronounced than men of his age. In this scenario, Jack is most likely:

Correct answer: A

Rationale: The correct answer is A: an XYY male. Individuals with XYY syndrome often exhibit increased height and more pronounced secondary male characteristics, such as thick facial hair. Choice B, Klinefelter syndrome (XXY), typically presents with less prominent male secondary sex characteristics due to the presence of an extra X chromosome. Choice C, XXY male, refers to Klinefelter syndrome, which does not align with the description of Jack having more pronounced male secondary sex characteristics. Choice D, Down syndrome, is caused by a trisomy of chromosome 21 and is not associated with the physical characteristics described in the scenario.

4. Which drug was marketed in the 1960s to pregnant women and caused birth defects such as missing or stunted limbs in infants?

Correct answer: C

Rationale: Thalidomide is the correct answer. Thalidomide was a drug marketed in the 1960s to pregnant women as a sedative and anti-nausea medication but tragically led to severe birth defects, including limb deformities, when taken during pregnancy. Progestin (Choice A) and Estrogen (Choice B) are hormones that are not associated with causing birth defects like Thalidomide. Oxytocin (Choice D) is a hormone that plays a role in labor and breastfeeding and is not known to cause birth defects like Thalidomide.

5. Which synthetic hormone is used to prevent miscarriages and can cause masculinization of the fetus?

Correct answer: C

Rationale: Progestin is the synthetic hormone used to prevent miscarriages. While it is beneficial in maintaining pregnancy, in some cases, it can lead to masculinization of the fetus. Testosterone (Choice A) and estrogen (Choice B) are not typically used to prevent miscarriages and do not cause masculinization of the fetus in this context. Oxytocin (Choice D) is a hormone involved in labor and breastfeeding, but it is not used to prevent miscarriages nor does it cause masculinization of the fetus.

Similar Questions

Monozygotic (MZ) twins are known as fraternal twins.
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After meiosis, each new cell nucleus contains _____ chromosomes.

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