HESI Maternal Newborn

Correct Answer: D

Rationale: Huntington's disease is a fatal genetic neurologic disorder characterized by progressive nerve cell degeneration in the brain. It typically manifests in middle age with symptoms such as involuntary movements, cognitive decline, and psychiatric disturbances. Tay-Sachs disease (Choice A) is a genetic disorder that primarily affects the nervous system in early childhood, not middle age. Duchenne muscular dystrophy (Choice B) is a genetic disorder that primarily affects muscle function and usually presents in early childhood. Hemophilia (Choice C) is a genetic disorder related to blood clotting, and its onset is not typically in middle age.

Correct Answer: B

Rationale: The correct answer is B: Adenine. In the structure of DNA, adenine pairs with thymine through hydrogen bonding, forming one of the complementary base pairs that make up the double helix structure of DNA. Cytosine pairs with guanine, not thymine. Rhodamine and serine are not DNA bases and do not participate in DNA base pairing. Therefore, choices A, C, and D are incorrect.

Correct Answer: A

Rationale: The correct answer is A: TRUE. Advanced parental age, particularly maternal age, is associated with an increased risk of Down's syndrome in offspring. As parents get older, the likelihood of having a child with Down's syndrome increases. Choices B, C, and D are incorrect because the risk of Down's syndrome is known to rise with parental age, especially maternal age, due to the increased likelihood of chromosomal abnormalities during egg formation.

Correct Answer: C

Rationale: Out of millions of sperm released during ejaculation, only a small fraction, about 1 in 1,000, will approach the ovum. This statement is true as sperm face many obstacles and challenges on their journey to reach and fertilize an ovum. Choice A is incorrect because the average count of sperm in an ejaculate is typically in the millions, not billions. Choice B is incorrect as sperm do not find the ovum by following the current of fluid; they navigate using other mechanisms. Choice D is incorrect because while some sperm may move randomly in the vagina, the ones that approach the ovum do so through a more purposeful and directed movement.

Correct Answer: C

Rationale: The correct answer is C. Mutations can occur due to environmental influences such as radiation, chemicals, or other external factors, leading to changes in the DNA sequence. Choice A is incorrect because mutations can also occur due to errors in DNA replication, not solely by chance. Choice B is incorrect as mutations affect the DNA sequence itself, not the production of specific cells. Choice D is incorrect because mutations involve changes in the DNA sequence and do not specifically involve the formation of the DNA structure.