HESI A2
Biology HESI A2 2024
1. How is mitosis different from meiosis?
- A. Mitosis is the process by which body cells are formed.
- B. Meiosis creates cells with half the chromosomes of the parent cell.
- C. Telophase occurs in both mitosis and meiosis.
- D. Spermatogenesis and oogenesis occur via meiosis.
Correct answer: B
Rationale: Meiosis is the type of cell division that creates cells with half the number of chromosomes compared to the parent cell. This is essential for sexual reproduction as it ensures that when the sex cells (sperm and egg) combine during fertilization, the resulting offspring has the correct number of chromosomes. In contrast, mitosis results in two identical daughter cells with the same number of chromosomes as the parent cell. Choice A is incorrect because mitosis is responsible for the division of body cells, not sex cells. Choice C is incorrect because telophase is a phase that occurs in both mitosis and meiosis. Choice D is incorrect because spermatogenesis and oogenesis involve meiosis, not mitosis.
2. Which is a byproduct of fermentation in muscle cells?
- A. Ethanol
- B. Pyruvic acid
- C. Lactic acid
- D. Oxygen
Correct answer: C
Rationale: Lactic acid is a byproduct of fermentation in muscle cells. During intense exercise or when oxygen is limited, muscle cells use anaerobic respiration to generate energy. This process breaks down glucose into lactic acid, which can cause muscle fatigue and soreness. Choice A, Ethanol, is not produced in muscle cells during fermentation. Choice B, Pyruvic acid, is an intermediate product in glucose metabolism but is not a byproduct of fermentation in muscle cells. Choice D, Oxygen, is not a byproduct of fermentation but a reactant in aerobic respiration.
3. The sum of all chemical reactions that occur in an organism is:
- A. product
- B. respiration
- C. metabolism
- D. synthesis
Correct answer: C
Rationale: Metabolism is the sum of all chemical reactions that occur within an organism to maintain life. It involves all the processes that break down molecules to release energy (catabolism) and build new molecules to support growth and maintenance (anabolism). Respiration refers specifically to the process of generating energy from the breakdown of glucose molecules. Synthesis is the creation of complex molecules from simpler ones. Therefore, metabolism is the most comprehensive term that encompasses all these processes within an organism.
4. In the scientific process, which of the following is a statement or explanation of certain events or happenings?
- A. hypothesis
- B. observation
- C. experiment
- D. conclusion
Correct answer: A
Rationale: A hypothesis is a statement or explanation of certain events or phenomena based on observations and prior knowledge. It is a testable prediction that guides the scientific investigation process. By formulating a hypothesis, scientists can make predictions and design experiments to gather data and test the validity of the hypothesis. Observations (choice B) involve gathering information through the senses. Experiments (choice C) are procedures carried out to support or refute a hypothesis. Conclusions (choice D) are deductions made based on the results of experiments and observations, but they are not the initial statement or explanation of events or happenings.
5. In an example of a male with hemophilia and a female carrier, what percentage of the offspring is predicted to be carriers only?
- A. 0%
- B. 25%
- C. 50%
- D. 100%
Correct answer: C
Rationale: In this scenario, the male offspring will inherit the X chromosome with the hemophilia gene from the mother, as males have one X chromosome inherited from their mother. The female offspring will inherit one normal X chromosome from the father and one X chromosome with the hemophilia gene from the mother, making them carriers of the hemophilia trait. Therefore, 50% of the offspring will be carriers only. Option A (0%) is incorrect as female offspring will inherit the X chromosome with the hemophilia gene from the mother. Option B (25%) is incorrect as the female offspring will not be unaffected. Option D (100%) is incorrect as not all offspring will be carriers, only the female offspring.
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