HESI A2
HESI A2 Biology 2024
1. Huntington’s disease is carried on the dominant allele. In a situation where two heterozygous parents have the disease, what percentage of their offspring are predicted to be disease-free?
- A. 0%
- B. 25%
- C. 50%
- D. 100%
Correct answer: B
Rationale: In this scenario, both parents are heterozygous for Huntington's disease, meaning each carries one dominant allele (representing the disease) and one recessive allele (representing no disease). When they have offspring, there is a 25% chance that each child will inherit two recessive alleles, making them disease-free. The Punnett square for two heterozygous parents (Hh x Hh) yields a 25% probability of offspring being homozygous recessive (hh) and therefore disease-free. Choice A (0%) is incorrect because there is a possibility of disease-free offspring. Choice C (50%) is incorrect as it represents the likelihood of being a carrier. Choice D (100%) is incorrect as all offspring will not be disease-free in this scenario.
2. What does the word UBIQUITOUS mean?
- A. Widespread
- B. Miniscule
- C. Invalid
- D. Unit
Correct answer: A
Rationale: The word UBIQUITOUS means something that is found everywhere or is very common. Therefore, the correct meaning for ubiquitous is 'widespread'. 'Miniscule' means very small, 'invalid' means not valid or acceptable, and 'unit' refers to a single entity or component, making them incorrect choices in the context of the word ubiquitous.
3. Select the phrase that makes the following sentence grammatically correct: 'Janet called her ____ run after a squirrel.'
- A. dog, who had
- B. dog that had
- C. dog, that had
- D. dog who had
Correct answer: A
Rationale: The correct answer is 'dog, who had.' The phrase 'dog, who had' correctly indicates that Janet called her dog to run after a squirrel. In this case, 'who had' provides additional information about the dog, making the sentence grammatically accurate. Choices B, C, and D are incorrect because they do not use the appropriate relative pronoun 'who' for referring to animals.
4. What is the function of platelets in the blood?
- A. Transporting oxygen
- B. Clotting blood
- C. Fighting infection
- D. Transporting nutrients
Correct answer: B
Rationale: Platelets, also known as thrombocytes, are responsible for clotting blood. When there is an injury, platelets help form blood clots to prevent excessive bleeding. This function is crucial in maintaining hemostasis and preventing hemorrhage. Choices A, C, and D are incorrect. Platelets do not transport oxygen, fight infection, or transport nutrients in the blood.
5. How should a researcher test the hypothesis that radiation from cell phones is significant enough to raise the temperature of water in a test tube?
- A. Dial a cell phone that rests beside a test tube of water, let it ring for two minutes, and record the temperature of the water before and after the two-minute interval.
- B. Dial a cell phone that rests beside a test tube of water; let it ring for two, three, and four minutes; and record the temperature of the water before and after each interval.
- C. Use three different brands of cell phone; dial each as it rests beside its own test tube of water, let it ring for two minutes, and record the temperature of the water before and after the two-minute interval.
- D. Use three different brands of cell phone, dial each and let one ring for two minutes, one for three minutes, and one for four minutes; record the temperature of the water before and after each interval.
Correct answer: A
Rationale: To test the hypothesis that radiation from cell phones raises the temperature of water in a test tube, the most appropriate method is to dial a cell phone next to a test tube of water, let it ring for a consistent two-minute interval, and record the temperature before and after. Choice A is correct because it provides a controlled approach to isolate the impact of the phone's radiation on the water temperature. Choices B, C, and D introduce additional variables that could confound the results. Choice B varies the duration of exposure, making it difficult to attribute temperature changes specifically to the radiation. Choice C introduces the factor of different cell phone brands, which could introduce variability not related to radiation. Choice D also varies exposure times and introduces the factor of multiple phone brands, making it harder to determine the direct impact of cell phone radiation on water temperature. Therefore, choice A is the most suitable option for this experiment.
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