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.

Correct Answer: A

Rationale: The correct answer is A: phenotype. A phenotype is the observable characteristics of an individual, which result from the interaction of their genotype with the environment. This interaction between genetics and the environment determines how genes are expressed and how traits are manifested in an individual. Choices B, C, and D are incorrect because chromosomes, alleles, and genotypes are components of an individual's genetic makeup, but they do not directly reflect the observable traits influenced by both genetics and the environment.

Correct Answer: B

Rationale: Applying a cap to the newborn's head is the correct action in this scenario. Newborns are at risk of heat loss due to their high surface area to volume ratio, and maintaining their body temperature is crucial to prevent hypothermia. Giving a warm bath can further increase heat loss and is not recommended. Repositioning the newborn may not address the primary concern of temperature regulation. While monitoring oxygen saturation is important, addressing thermal regulation takes precedence in this situation.

Correct Answer: B

Rationale: The correct answer is B: "Breast milk can be stored in a deep freezer for 12 months." This instruction is important for mothers returning to work to ensure a long-term storage option for breast milk. Choice A is incorrect because thawed breast milk should be used within 24 hours if stored in the refrigerator. Choice C is incorrect as breast milk can be kept at room temperature for only up to 4 hours. Choice D is incorrect as thawed breast milk that is unused should not be refrozen due to safety concerns.

Correct Answer: A

Rationale: Before meiosis, a sperm cell contains 46 chromosomes. This is because sperm cells, like other somatic cells, have a diploid number of chromosomes. During meiosis, the number of chromosomes is halved to 23 to combine with an egg cell during fertilization. Choice B is incorrect because a sperm cell carries either an X or a Y chromosome, not both (Choice D). Choice C is incorrect as sperm cells are generally smaller than egg cells, which is an adaptation that aids in motility and penetration of the egg during fertilization.