HESI A2
Biology HESI A2 2024
1. In an example of a male with hemophilia and a female carrier, what ratio of the offspring is predicted to have the disease?
- A. 0 female : 2 males
- B. 1 female : 0 males
- C. 1 female : 2 males
- D. 2 females : 1 male
Correct answer: C
Rationale: In this scenario, the male offspring will inherit the hemophilia trait from their mother due to the sex-linked inheritance pattern. The female offspring will inherit one X chromosome from their mother, becoming carriers of hemophilia. Therefore, the predicted ratio of offspring with the disease would be 1 female as a carrier and 2 males with hemophilia. Choice A is incorrect because there would be male offspring with the disease. Choice B is incorrect as there would be male offspring with hemophilia. Choice D is incorrect as it does not reflect the inheritance pattern of hemophilia.
2. 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.
3. Imagine that two parents both carry the recessive gene for cystic fibrosis. Any homozygous recessive offspring will manifest the disease. What percentage of the offspring is predicted to be carriers but not manifest the disease?
- A. 0%
- B. 25%
- C. 50%
- D. 100%
Correct answer: B
Rationale: When both parents carry the recessive gene for cystic fibrosis (homozygous recessive), there is a 25% chance for each offspring to inherit two recessive alleles and, therefore, manifest the disease. There is also a 50% chance for each offspring to inherit one recessive allele and one dominant allele, making them carriers of the disease but not manifest it. Therefore, 25% of the offspring are predicted to be carriers but not manifest the disease. Choice A (0%) is incorrect because there is a portion of offspring that will be carriers. Choice C (50%) is incorrect as this percentage corresponds to carriers who will not manifest the disease. Choice D (100%) is incorrect as not all offspring will be carriers and not manifest the disease.
4. What is represented by this formula: 6COâ‚‚ + 6Hâ‚‚O → C₆Hâ‚â‚‚O₆ + 6Oâ‚‚?
- A. Glycolysis
- B. Cellular respiration
- C. Photosynthesis
- D. Electronic transport
Correct answer: C
Rationale: The formula represents the process of photosynthesis, where carbon dioxide (COâ‚‚) and water (Hâ‚‚O) are converted into glucose (C₆Hâ‚â‚‚O₆) and oxygen (Oâ‚‚) using light energy. This process is essential for plants and some microorganisms to produce food and oxygen. Glycolysis and cellular respiration involve breaking down glucose to produce energy, and the electron transport chain is part of cellular respiration, not photosynthesis.
5. What is the purpose of phloem tissue in plant stems?
- A. It conducts water up through the stem.
- B. It conducts the energy of light to leaves.
- C. It conducts food throughout the plant.
- D. It conducts carbon dioxide throughout the plant.
Correct answer: C
Rationale: The purpose of phloem tissue in plant stems is to conduct food, particularly sugars produced in the leaves during photosynthesis, throughout the plant. The phloem transports these organic compounds to various parts of the plant where they are needed for growth and energy. Choice A is incorrect because water is primarily transported by xylem tissue, not phloem. Choice B is incorrect as the energy of light is captured by chlorophyll in the process of photosynthesis, not conducted by phloem. Choice D is incorrect because carbon dioxide is mainly absorbed through the leaves and transported to other parts of the plant through diffusion, not by phloem.
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