HESI A2
HESI A2 Biology 2024
1. Which is not a product of the Krebs cycle?
- A. ATP
- B. Carbon dioxide
- C. Glucose
- D. NADH
Correct answer: C
Rationale: Glucose is not a direct product of the Krebs cycle. Glucose is a starting molecule that undergoes glycolysis outside the mitochondria to produce pyruvate, which then enters the mitochondrial matrix to participate in the Krebs cycle. The Krebs cycle primarily generates ATP, carbon dioxide, and NADH as products. Choices A, B, and D are all products of the Krebs cycle, making them incorrect answers.
2. Where is the genetic code for each person stored?
- A. RNA
- B. DNA
- C. Nucleus
- D. Chromosomes
Correct answer: B
Rationale: The genetic code for each person is stored in DNA. DNA carries all the hereditary information, including unique traits and characteristics. RNA (Choice A) is involved in protein synthesis but does not hold the complete genetic code. The nucleus (Choice C) is a cellular organelle that houses the DNA, but it is not the genetic code itself. Chromosomes (Choice D) are structures made of DNA and proteins, but the genetic code is specifically encoded in the DNA molecule.
3. Which organism reproduces via binary fission?
- A. Mushroom
- B. Blue whale
- C. Rainbow trout
- D. Salmonella
Correct answer: D
Rationale: The correct answer is D, Salmonella. Salmonella bacterium reproduces via binary fission, a form of asexual reproduction where the cell divides into two daughter cells with identical genetic material. This process is common among bacteria and single-celled organisms. Mushrooms reproduce through spores, blue whales and rainbow trout reproduce sexually, involving the fusion of male and female gametes. Therefore, choices A, B, and C are incorrect as they do not reproduce through binary fission.
4. Tonicity refers to the movement of:
- A. Water
- B. Solute
- C. Cells
- D. None of the above
Correct answer: A
Rationale: Tonicity refers to the movement of water across a membrane in response to differences in solute concentration. In a hypertonic solution, where there is a higher concentration of solutes outside the cell, water will move out of the cell to try to reach equilibrium. In a hypotonic solution, where there is a lower concentration of solutes outside the cell, water will move into the cell to balance the concentrations. Cells and solutes themselves do not actively move in response to tonicity; it is the movement of water that helps achieve equilibrium. Therefore, the correct answer is water (Choice A). Choices B, C, and D are incorrect as tonicity specifically refers to water movement and not the movement of solutes, cells, or none of the above.
5. The fur color in a population of dogs is controlled by two alleles: black (B) and tan (b). The black allele exhibits complete dominance. If the phenotype of the dog is tan fur, what is its genotype?
- A. BB
- B. Bb
- C. bb
- D. Not enough information
Correct answer: C
Rationale: The correct answer is C: "bb." Since tan fur is the recessive trait controlled by the allele 'b,' the only possible genotype for a dog with tan fur is 'bb.' If a dog had the genotype 'BB' or 'Bb,' the dominant trait (black fur) would be expressed, not tan fur. Choice D, 'Not enough information,' is incorrect because based on the information provided, we can deduce the genotype of a dog with tan fur.
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