Correct Answer: C

Rationale: Turner syndrome is a chromosomal disorder in females characterized by short stature and underdeveloped ovaries, resulting in low estrogen production. This leads to symptoms such as delayed puberty and infertility. Choice A is incorrect because the chromosomal abnormality in Turner syndrome does not affect the thymine-cytosine ratio. Choice B is incorrect as females with Turner syndrome are typically shorter than average. Choice D is incorrect as Turner syndrome does not increase the likelihood of giving birth to twins.

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.

Correct Answer: C

Rationale: Turner syndrome is a chromosomal disorder in females characterized by short stature and underdeveloped ovaries, resulting in low estrogen production. This leads to symptoms such as delayed puberty and infertility. Choice A is incorrect because the chromosomal abnormality in Turner syndrome does not affect the thymine-cytosine ratio. Choice B is incorrect as females with Turner syndrome are typically shorter than average. Choice D is incorrect as Turner syndrome does not increase the likelihood of giving birth to twins.

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.

Correct Answer: A

Rationale: At 14 weeks of gestation, the uterus is still relatively low in the abdomen. Placing the Doppler midline 2 to 3 cm above the symphysis pubis is appropriate for assessing the fetal heart rate. This location allows for better detection of the fetal heart tones as the uterus is at a lower position during this stage of pregnancy. Placing the Doppler on the left upper abdomen would not be ideal at 14 weeks gestation as the uterus is not yet at that level. Placing it two fingerbreadths above the umbilicus or lateral at the xiphoid process would also not be accurate for locating the fetal heart rate at this stage of gestation.