HESI A2
Biology HESI A2 Practice Exam
1. In nature, water vapor becomes liquid water through the process of ___________.
- A. condensation
- B. sublimation
- C. precipitation
- D. absorption
Correct answer: A
Rationale: In nature, water vapor becomes liquid water through the process of condensation. Condensation occurs when water vapor cools and changes its state from a gas to a liquid, forming droplets that we commonly see as water droplets on surfaces or clouds in the sky. Sublimation refers to the transition from a solid to a gas without passing through the liquid phase. Precipitation is the process where water in the atmosphere falls to the ground as rain, snow, sleet, or hail. Absorption is the process of one substance being taken in by another.
2. 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.
3. Physical factors such as temperature and pH can alter enzyme activity because they have an effect on the enzyme's ___________.
- A. acidity
- B. shape
- C. chemistry
- D. substrate
Correct answer: B
Rationale: Physical factors such as temperature and pH can alter enzyme activity by affecting the enzyme's shape. Enzymes rely on their specific shapes to function properly and catalyze reactions. Any changes in temperature or pH can disrupt these shapes, causing the enzyme to become denatured and lose its functionality. Therefore, alterations in temperature and pH can impact enzyme activity by directly affecting their shapes. Choices A, C, and D are incorrect because while pH can affect acidity and chemical properties of the enzyme, and temperature can influence the enzyme-substrate interaction, the primary reason for enzyme activity alteration due to temperature and pH is the change in the enzyme's shape.
4. Phenotype refers to the _ of an individual.
- A. Genetic makeup
- B. Actual physical appearance
- C. Recessive alleles
- D. None of the above
Correct answer: B
Rationale: Phenotype refers to the actual physical appearance and characteristics of an individual, which are determined by the interaction of both genetic makeup (genotype) and environmental factors. It includes visible traits such as height, eye color, and hair type. Choice A, genetic makeup, refers to the genotype, which is the genetic constitution of an organism. Choice C, recessive alleles, is a specific type of gene variant and does not encompass the entire concept of phenotype. Choice D, none of the above, is incorrect as phenotype does refer to the actual physical appearance of an individual.
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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