HESI A2
HESI A2 Biology Practice Test
1. When the genotype consists of a dominant and a recessive allele, the phenotype will be like the _ allele.
- A. Dominant
- B. Recessive
- C. Both
- D. Neither
Correct answer: A
Rationale: When the genotype consists of a dominant and a recessive allele, the phenotype will be like the dominant allele. This is because dominant alleles typically mask the expression of recessive alleles. Therefore, the dominant allele will be expressed in the phenotype in most basic cases. The recessive allele will only be expressed phenotypically if the individual is homozygous recessive. Choice B, 'Recessive,' is incorrect because the phenotype will not be like the recessive allele in this case. Choice C, 'Both,' is incorrect because in simple dominant-recessive inheritance, the dominant allele will overshadow the recessive allele. Choice D, 'Neither,' is incorrect as the phenotype will resemble the dominant allele.
2. Which of the following are considered the most important molecules in biology?
- A. Carbohydrates, lipids, protein, and nucleic acids
- B. Carbohydrates, lipids, protein, and calcium
- C. Carbohydrates, lipids, protein, and sulfur
- D. Carbohydrates, lipids, protein, and iron
Correct answer: A
Rationale: The correct answer is A: Carbohydrates, lipids, protein, and nucleic acids are considered the most important molecules in biology. Carbohydrates are essential for providing energy, lipids for storing energy and forming cell membranes, proteins for various structural and functional roles, and nucleic acids (DNA and RNA) for storing genetic information. Choices B, C, and D are incorrect because while carbohydrates, lipids, and proteins are crucial biomolecules, calcium, sulfur, and iron are not considered among the most important molecules in biology.
3. How is the plasma membrane arranged?
- A. In a single layer made of proteins
- B. In a double layer made of proteins
- C. In a single layer of phospholipids
- D. In a double layer of phospholipids
Correct answer: D
Rationale: The plasma membrane is arranged in a double layer of phospholipids, known as a phospholipid bilayer. This structure consists of two layers of phospholipid molecules with hydrophilic heads facing the exterior and hydrophobic tails facing the interior, providing a semipermeable barrier for the cell. Choice A is incorrect because the plasma membrane is not made of a single layer of proteins. Choice B is incorrect as the double layer is composed of phospholipids, not proteins. Choice C is incorrect as the plasma membrane is not made of a single layer of phospholipids but rather a double layer.
4. How does water affect the temperature of a living thing?
- A. Water increases temperature.
- B. Water keeps temperature stable.
- C. Water decreases temperature.
- D. Water does not affect temperature.
Correct answer: B
Rationale: Water has a high specific heat capacity, which means it can absorb and release large amounts of heat with minimal temperature change. This property helps water regulate the temperature of living things by maintaining a stable environment. Choice A is incorrect because water does not consistently increase temperature, but rather helps in temperature regulation. Choice C is incorrect as water doesn't typically decrease temperature in living organisms. Choice D is incorrect since water does play a crucial role in regulating temperature.
5. From which component do RNA and DNA derive their names?
- A. From the sugar each contains
- B. From the structure of their nucleotides
- C. From the information they transfer
- D. From their formative processes
Correct answer: A
Rationale: RNA and DNA derive their names from the sugar each contains. RNA stands for Ribonucleic Acid, with 'ribo' indicating the ribose sugar in its structure. DNA stands for Deoxyribonucleic Acid, with 'deoxyribo' referring to the deoxyribose sugar in its structure. The sugars in RNA and DNA molecules distinguish them and are the basis for their names. Choices B, C, and D are incorrect as they do not accurately explain how RNA and DNA derive their names.
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