HESI A2
HESI A2 Biology 2024
1. 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.
2. What is DNA made of?
- A. Proteins
- B. Nucleotides
- C. Lipids
- D. Carbohydrates
Correct answer: B
Rationale: DNA is made up of nucleotides, which are the building blocks of genetic material. Choice A (Proteins) is incorrect because while proteins play a crucial role in the body, they are not the building blocks of DNA. Choice C (Lipids) and Choice D (Carbohydrates) are also incorrect as they are not the primary components of DNA.
3. Why is homeostasis necessary?
- A. It maintains temperature
- B. It maintains pH
- C. It maintains glucose levels
- D. All of the above
Correct answer: D
Rationale: Homeostasis is necessary because it ensures the maintenance of a stable, relatively constant internal environment. This includes regulating various factors such as temperature, pH levels, and glucose levels to support optimal bodily functions and overall health. Choices A, B, and C are all correct as they represent key aspects of homeostasis that contribute to maintaining the body's internal balance.
4. What happens to messenger RNA when it reaches the cytoplasm?
- A. It attaches to a ribosome.
- B. It unzips, exposing nitrogen bases.
- C. It pairs with the DNA bases.
- D. It pulls free of the DNA strand.
Correct answer: A
Rationale: Messenger RNA (mRNA) carries genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm. When mRNA reaches the cytoplasm, it attaches to a ribosome. The ribosome functions as the site for protein synthesis through translation, where the genetic code carried by mRNA is read and translated into a specific sequence of amino acids. Choices B, C, and D are incorrect because mRNA does not unzip, expose nitrogen bases, pair with DNA bases, or pull free of the DNA strand in the cytoplasm. The primary function of mRNA in the cytoplasm is to serve as a template for protein synthesis by binding to ribosomes.
5. Which is true of gametes?
- A. They are diploid cells
- B. They are haploid cells
- C. They are somatic
- D. A & C are true
Correct answer: B
Rationale: Gametes are sex cells (sperm and eggs) that are involved in sexual reproduction. They are haploid cells, meaning they have half the number of chromosomes (n) compared to diploid cells. This is necessary for the formation of a diploid zygote when two gametes unite during fertilization. Somatic cells are non-reproductive cells in the body, so they are not gametes. Choice A is incorrect because gametes are not diploid but haploid. Choice C is incorrect because gametes are not somatic cells.
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