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. Which molecule is primarily responsible for storing energy in cells?
- A. Glucose
- B. ATP
- C. Fatty acids
- D. Starch
Correct answer: B
Rationale: ATP is the correct answer because it is the molecule responsible for storing and providing energy in cells. Glucose is a source of energy but not primarily for storage. Fatty acids are more involved in energy production through oxidation. Starch is a polysaccharide used for energy storage in plants.
3. Enzymes can _ reactions.
- A. Catalyze
- B. Inhibit
- C. Stop
- D. None of the above
Correct answer: A
Rationale: Enzymes function as catalysts that promote and accelerate chemical reactions in biological systems. They do this by lowering the activation energy required for the reactions to occur, thereby speeding up the process without being consumed in the reaction. Enzymes facilitate reactions rather than inhibiting or stopping them. Therefore, the correct answer is 'Catalyze.' 'Inhibit' and 'Stop' are incorrect because enzymes do not hinder or halt reactions but rather enhance them.
4. Why are bacteria and blue-green algae often classified together?
- A. Both are gymnosperms.
- B. Both are prokaryotes.
- C. Both are autotrophs.
- D. Both are pathogens.
Correct answer: B
Rationale: Bacteria and blue-green algae (cyanobacteria) are often classified together because they are both prokaryotes. Prokaryotes are unicellular organisms that lack a membrane-bound nucleus and other membrane-bound organelles. This characteristic distinguishes them from eukaryotic organisms, which have these membrane-bound structures. Choice A is incorrect because gymnosperms are seed-producing plants with naked seeds, not bacteria or blue-green algae. Choice C is incorrect because being an autotroph (able to produce its own food) is not a reason for classifying them together. Choice D is incorrect because not all bacteria and blue-green algae are pathogens; many of them are beneficial or neutral to other organisms.
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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