HESI RN
Biology Test
1. Binary fission is a type of asexual reproduction. Which of the following occurs during the binary fission process?
- A. The chromosomes bind to the plasma membrane
- B. The chromosomes attach to the spindle formed along the axis
- C. The chromosomes gather in the center of the cell
- D. The chromosomes begin to separate
Correct answer: A
Rationale: The correct answer is A. In binary fission, the chromosomes bind to the plasma membrane before the cell splits into two. This initial step ensures that each daughter cell receives a complete set of genetic material. Choice B is incorrect because the spindle apparatus is characteristic of eukaryotic cell division (mitosis), not prokaryotic binary fission. Choice C is incorrect as chromosomes do not necessarily gather in the center of the cell during binary fission. Choice D is incorrect because the chromosomes do not begin to separate in binary fission; they replicate and then move to opposite ends of the cell before division.
2. What characteristic of water allows for hydrogen bonding between molecules?
- A. Its covalent bonds
- B. Its cohesive properties
- C. Its high specific heat
- D. Its polar nature
Correct answer: D
Rationale: The correct answer is D: Its polar nature. Water is a polar molecule with a partial positive charge on hydrogen atoms and a partial negative charge on oxygen atoms. This polarity allows water molecules to form hydrogen bonds with each other. Choice A, covalent bonds, is incorrect because while water indeed has covalent bonds, they do not directly enable hydrogen bonding. Choice B, cohesive properties, is incorrect as cohesion refers to water's ability to stick to other substances, not the specific characteristic that allows for hydrogen bonding. Choice C, high specific heat, is also incorrect as it refers to water's ability to resist changes in temperature, not its property that leads to hydrogen bonding.
3. Phagocytes in the immune system are responsible for the biological action of which of the following?
- A. Secreting
- B. Consuming
- C. Altering
- D. Building
Correct answer: B
Rationale: The correct answer is B: Consuming. Phagocytes are cells that engulf and digest pathogens, dead cells, and other harmful particles, playing a crucial role in the immune system's defense. Phagocytes do not secrete substances, alter particles, or build structures; their primary function is to consume and eliminate harmful entities.
4. Which of the following is not one of the four nitrogenous bases that make up the DNA structure?
- A. Adenine
- B. Guanine
- C. Uracil
- D. Thymine
Correct answer: C
Rationale: The correct answer is C: Uracil. Uracil is found in RNA, not DNA. The four nitrogenous bases in DNA are adenine, thymine, cytosine, and guanine. Choice A, Adenine, is a nitrogenous base in DNA. Choice B, Guanine, is another nitrogenous base in DNA. Choice D, Thymine, is also one of the four nitrogenous bases in DNA. Therefore, the correct answer is Uracil (Choice C).
5. During which stage of mitosis does the nuclear envelope begin to disappear and the chromosomes start attaching to the spindle forming along the cell's axis?
- A. Prometaphase
- B. Metaphase
- C. Anaphase
- D. Prophase
Correct answer: A
Rationale: The correct answer is A, Prometaphase. During prometaphase, the nuclear envelope disintegrates, and chromosomes start attaching to spindle fibers. In metaphase, chromosomes align in the middle of the cell. Anaphase is characterized by the separation of sister chromatids, and prophase involves the condensation of chromosomes and the beginning of spindle formation.
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