HESI A2
HESI A2 Biology Practice Test
1. A child is sick. They have a body temperature that exceeds 37ÂșC. The body senses this and begins to sweat in order to lower the temperature. What is this an example of?
- A. Positive feedback loop
- B. Negative feedback loop
- C. Both
- D. None of the above
Correct answer: B
Rationale: This is an example of a negative feedback loop. In a negative feedback loop, the body's response (sweating) works to counteract the initial stimulus of a high body temperature by cooling the body down. The goal is to return the body to homeostasis, maintaining a stable internal environment. Positive feedback loops amplify the initial stimulus rather than counteracting it, which is not the case here. Therefore, choices A and C are incorrect. Choice D is also incorrect as the situation described fits the characteristics of a negative feedback loop.
2. What type of cell is an animal cell?
- A. Prokaryotic
- B. Eukaryotic
- C. Plant Cell
- D. Bacterial Cell
Correct answer: B
Rationale: The correct answer is B, eukaryotic. Animal cells are classified as eukaryotic cells because they contain membrane-bound organelles such as the nucleus, mitochondria, and endoplasmic reticulum. Choice A, prokaryotic, is incorrect as prokaryotic cells lack membrane-bound organelles. Choice C, Plant Cell, is incorrect as the question specifically asks about animal cells. Choice D, Bacterial Cell, is incorrect as bacteria are prokaryotic cells.
3. What happens during anaphase?
- A. Chromosomes move to opposite ends of the spindle.
- B. Nuclear membrane and nucleoli disintegrate.
- C. Chromatids line up at the center of the spindle.
- D. Nuclear membrane and nucleoli form.
Correct answer: A
Rationale: During anaphase, the sister chromatids, joined at the centromere, separate and move towards opposite ends of the spindle apparatus. This movement ensures that each daughter cell receives an identical set of chromosomes. Choice B is incorrect as the disintegration of the nuclear membrane and nucleoli occurs during prophase. Choice C is incorrect as chromatids align at the center of the spindle during metaphase, not anaphase. Choice D is incorrect as the formation of the nuclear membrane and nucleoli occurs during telophase, not anaphase.
4. Select the strand of DNA that would match this segment: ACTTGCA
- A. TGAACGT
- B. GACCATG
- C. ACTTGCA
- D. None of the above
Correct answer: A
Rationale: The correct match for the DNA segment ACTTGCA is TGAACGT. In DNA, adenine (A) always pairs with thymine (T), and cytosine (C) always pairs with guanine (G). Therefore, the complementary strand to ACTTGCA should be TGAACGT, making choice A the correct answer. Choice B (GACCATG) does not follow the base pairing rules; hence, it is incorrect. Choice C (ACTTGCA) is the original segment, not its complementary strand. Choice D is incorrect as well because a matching strand does exist.
5. During which phase of cell division do the chromosomes replicate?
- A. Prophase
- B. Interphase
- C. Anaphase
- D. Telophase
Correct answer: B
Rationale: Chromosomes replicate during the interphase of the cell cycle. Interphase is the phase where the cell prepares for division by undergoing various activities such as growth, DNA replication, and protein synthesis. During DNA replication in interphase, each chromosome in the cell is duplicated to form two sister chromatids, which are then separated during cell division. Prophase is the phase where the chromosomes condense, and the nuclear envelope breaks down. Anaphase is the phase where sister chromatids are pulled apart towards opposite poles of the cell. Telophase is the phase where the nuclear envelope reforms, and chromosomes begin to decondense.
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