What causes cystic fibrosis?

Correct Answer: C

Rationale: Cystic fibrosis is a genetic disorder caused by inheriting two copies of a recessive gene, one from each parent. This means that both parents must carry at least one copy of the faulty gene for a child to inherit the condition. Choice A is incorrect because cystic fibrosis is not linked to the sex chromosomes. Choice B is incorrect as cystic fibrosis is not caused by an abnormality in the 21st pair of chromosomes but by a specific gene mutation. Choice D is also incorrect as cystic fibrosis is not related to the Y chromosome, which is specific to males.

Correct Answer: D

Rationale: The correct answer is D: WBC count 32,000/mm3. A WBC count of 32,000/mm3 is significantly elevated in a newborn and could indicate an infection, which needs immediate attention and intervention. High white blood cell counts in newborns can be concerning as they may suggest an ongoing infection or other underlying issues that require prompt medical evaluation and treatment. Choices A, B, and C are within normal ranges for a newborn and would not typically warrant immediate reporting to the provider. Hgb levels of 20 g/dL (Choice A) are high for newborns, but this is not as concerning as a significantly elevated WBC count. Bilirubin levels of 2 mg/dL (Choice B) are within normal limits for a newborn and do not indicate immediate issues. Platelet count of 200,000/mm3 (Choice C) is also within the normal range for a newborn and would not require immediate reporting.

Correct Answer: A

Rationale: Post-term newborns often have longer nails that extend over the tips of their fingers due to the extended gestation period. This occurs because the baby continues to grow in utero past the typical 40 weeks of gestation. Choices B, C, and D are incorrect as large deposits of subcutaneous fat, pale translucent skin, and a thin covering of fine hair on shoulders and back are not typically associated with post-term newborns. Longer nails are a common finding in post-term newborns due to the prolonged time spent in the womb, allowing for more nail growth compared to infants born at term.

Correct Answer: B

Rationale: The correct statement regarding menstruation is that during this time, an unfertilized egg is discharged along with the shedding of the uterine lining. Choice A is incorrect because the endometrium is shed during menstruation. Choice C is incorrect as menstruation does not prevent a female from engaging in sexual activity with her partner. Choice D is incorrect as a fertilized egg does not undergo mitosis during menstruation but rather implants in the uterine lining for further development.

Correct Answer: C

Rationale: The endoderm is the correct answer. It is the innermost layer of the embryo that gives rise to organs such as the lungs, digestive system, liver, and pancreas. The neural tube (Choice A) forms the brain and spinal cord, not the lungs or digestive system. Mesoderm (Choice B) develops into structures like muscles, bones, and circulatory system, not the lungs or digestive system. The umbilical cord (Choice D) serves as a connection between the embryo and the placenta, providing nutrients and oxygen, but it is not the layer from which lungs and digestive system develop.