HESI A2
Biology HESI A2 Practice Test
1. 72 chromosomes undergo meiosis. How many chromosomes will be in each gamete?
- A. 18
- B. 36
- C. 72
- D. 144
Correct answer: A
Rationale: During meiosis, the number of chromosomes is halved in each gamete. Since 72 chromosomes undergo meiosis, each gamete will contain half of that number, which is 36 chromosomes. Therefore, the correct answer is 18 chromosomes in each gamete. Choice B (36 chromosomes) is incorrect because it represents the total number of chromosomes that undergo meiosis, not the number in each gamete. Choice C (72 chromosomes) is incorrect as it represents the initial number of chromosomes, not the number in each gamete after meiosis. Choice D (144 chromosomes) is incorrect as it doubles the initial number of chromosomes, which is not the outcome of meiosis.
2. Which of the following is true of homozygous traits?
- A. They are haploid
- B. They are denoted AA
- C. They are denoted aa
- D. They are denoted Aa
Correct answer: B
Rationale: Homozygous traits have two identical forms of the gene, either both dominant (AA) or both recessive (aa). Therefore, choices B and C are true for homozygous traits. Choice A is incorrect because being haploid refers to having a single set of chromosomes, not necessarily homozygous traits. Choice D is incorrect as homozygous traits have identical alleles, so they are not denoted as Aa.
3. Why is it important for cells to undergo mitosis?
- A. mitosis allows for reproduction with male and female gametes
- B. mitosis increases variation within the species
- C. mitosis produces cells that are different from the parent cell
- D. mitosis produces cells for growth and repair of body tissue
Correct answer: D
Rationale: It is important for cells to undergo mitosis because it produces cells for the growth and repair of body tissues. Mitosis allows for the formation of genetically identical daughter cells, ensuring proper function and maintenance of the organism's body. By producing new cells, mitosis helps in the replenishment of damaged or worn-out tissue and supports overall growth and development. Choices A, B, and C are incorrect because mitosis is not directly related to reproduction with male and female gametes, increasing variation within the species, or producing cells different from the parent cell. These functions are more associated with meiosis, which is specifically for sexual reproduction and genetic diversity.
4. Why can animal cells use a contractile ring but plant cells cannot?
- A. Plant cells can use both methods to divide
- B. Animal cells divide faster, requiring them to pinch apart
- C. Plant cells are too rigid to use a contractile ring
- D. N/A
Correct answer: C
Rationale: Plant cells have a rigid cell wall surrounding them, which prevents them from using a contractile ring for cell division. The rigid cell wall requires plant cells to form a cell plate during cell division instead of pinching apart like animal cells with a contractile ring. Choice A is incorrect because plant cells cannot use a contractile ring due to their rigid cell wall. Choice B is incorrect as the speed of cell division is not the primary reason for the difference in cell division mechanisms between plant and animal cells. Choice D is not applicable as plant cells indeed have a specific limitation in using a contractile ring for cell division.
5. Why does cellular respiration happen?
- A. Cells can copy DNA
- B. Cells can breathe
- C. Cells can convert nutrients to energy
- D. Cells can divide
Correct answer: C
Rationale: Cellular respiration is the process through which cells break down nutrients such as glucose to produce ATP (adenosine triphosphate), the energy currency of the cell. This process allows cells to extract energy from food molecules and use it for various cellular activities and functions. Choices A, B, and D are incorrect because cellular respiration is specifically about converting nutrients to energy, not about DNA copying, breathing, or cell division.
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