HESI A2
HESI A2 Biology 2024
1. 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.
2. Which cellular structure is found in animal cells but not in plant cells?
- A. Centriole
- B. Cytoplasm
- C. Vacuole
- D. Golgi apparatus
Correct answer: A
Rationale: The correct answer is A, Centriole. Centrioles are found in animal cells but not in plant cells. They play a crucial role in organizing microtubules during cell division, aiding in the formation of the mitotic spindle. Plant cells lack centrioles; instead, they utilize microtubule organizing centers to perform similar functions during cell division. Choices B, C, and D are incorrect because cytoplasm is a part of both animal and plant cells, vacuoles are found in plant cells and some animal cells, and the Golgi apparatus is present in both types of cells.
3. Which organelle is found in protists but not in monerans?
- A. Golgi apparatus
- B. Chromosome
- C. Cytoplasm
- D. Cell membrane
Correct answer: A
Rationale: The Golgi apparatus is the correct answer. The Golgi apparatus is a cellular organelle responsible for processing and packaging proteins before they are transported to their final destination. Protists, being eukaryotic organisms, have membrane-bound organelles including the Golgi apparatus, which are absent in monerans. Monerans are prokaryotic organisms that lack membrane-bound structures such as the Golgi apparatus. Choices B, C, and D are incorrect as chromosomes, cytoplasm, and cell membranes are present in both protists and monerans.
4. ___________ is a symbiotic relationship in which one organism benefits and the other is not affected.
- A. Mutualism
- B. Parasitism
- C. Commensalism
- D. Competition
Correct answer: C
Rationale: The correct answer is 'Commensalism.' In commensalism, one organism benefits from the relationship while the other is neither helped nor harmed. This type of symbiotic relationship is characterized by one organism deriving a benefit, such as food or shelter, without impacting the other organism in any significant way. Choice A, 'Mutualism,' is a symbiotic relationship in which both organisms benefit. Choice B, 'Parasitism,' is a symbiotic relationship in which one organism benefits at the expense of the other. Choice D, 'Competition,' refers to a relationship in which organisms compete for limited resources, with both being affected in terms of access to resources.
5. How do green plants use nitrates in the nitrogen cycle?
- A. To synthesize proteins
- B. To store food
- C. To decompose ammonia
- D. To break down nitrites
Correct answer: A
Rationale: Green plants use nitrates in the nitrogen cycle to synthesize proteins. Nitrogen is an essential component of amino acids, which are the building blocks of proteins. Plants take up nitrates from the soil through their roots and incorporate nitrogen into their proteins through the process of protein biosynthesis. This helps in their growth, development, and overall health. Choice B, 'To store food,' is incorrect because nitrates are primarily used for protein synthesis, not food storage. Choice C, 'To decompose ammonia,' is incorrect as plants do not decompose ammonia but rather utilize it through nitrification. Choice D, 'To break down nitrites,' is incorrect as plants typically convert nitrites into nitrates through a process called nitrate assimilation for protein synthesis.
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