downs syndrome is caused by

HESI LPN

HESI Maternal Newborn

1. What causes Down's syndrome?

A. Alcohol abuse by the mother at the time of conception.
B. Sex-linked chromosomal abnormalities.
C. An extra chromosome on the 21st pair.
D. Drug abuse by the mother during pregnancy.

Correct answer: C

Rationale: Down's syndrome, also known as trisomy 21, is caused by the presence of an extra chromosome on the 21st pair. Choice A is incorrect as alcohol abuse is not the cause of Down's syndrome. Choice B is incorrect because Down's syndrome is not related to sex-linked chromosomal abnormalities. Choice D is also incorrect as drug abuse by the mother during pregnancy is not the cause of Down's syndrome.

2. Which of the following is a fatal genetic neurologic disorder whose onset is in middle age?

A. Tay-Sachs disease
B. Duchenne muscular dystrophy
C. Hemophilia
D. Huntington’s disease

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.

3. A healthcare provider is assessing a newborn immediately following a vaginal birth. For which of the following findings should the provider intervene?

A. Molding
B. Vernix Caseosa
C. Acrocyanosis
D. Sternal retractions

Correct answer: D

Rationale: Sternal retractions in a newborn indicate respiratory distress and require immediate intervention. This finding suggests the newborn is having difficulty breathing and needs prompt attention to ensure adequate oxygenation. Molding, the overlapping of fetal skull bones during birth, is a normal and expected process that does not require intervention. Vernix Caseosa, the protective white substance on the skin, and Acrocyanosis, the bluish discoloration of extremities, are both common and benign findings in newborns that do not necessitate immediate action. Therefore, the healthcare provider should focus on addressing sternal retractions to manage the respiratory distress effectively.

4. Which of the following processes happen during mitosis?

A. Strands of deoxyribonucleic acid (DNA) break apart.
B. Adenine combines with its appropriate partner, cytosine.
C. Sperm and ova cells are created.
D. Twenty-three chromosomes are created.

Correct answer: A

Rationale: The correct process that happens during mitosis is the breaking apart, replication, and division of DNA strands into two new cells, each with the same number of chromosomes as the original cell. Choice B is incorrect because it describes base pairing in DNA, not a process specific to mitosis. Choice C is incorrect as the creation of sperm and ova cells is related to meiosis, not mitosis. Choice D is incorrect because chromosomes are not created during mitosis; they are replicated and divided equally between the daughter cells.

5. Chromosomes are _____ structures found in cells.

A. rod-shaped
B. circular
C. cone-shaped
D. octagonal

Correct answer: A

Rationale: Chromosomes are rod-shaped structures that carry genetic information in the form of DNA. They are typically seen as elongated structures when visualized under a microscope. Choice B, circular, is incorrect as chromosomes do not have a circular shape; they are linear. Choice C, cone-shaped, is not accurate as chromosomes do not resemble cones in any way. Choice D, octagonal, is also incorrect as chromosomes do not have an octagonal appearance. Therefore, the correct answer is A, rod-shaped, which accurately describes the shape of chromosomes.