HESI RN
Biology Practice Test
1. In meiosis, the chromosome number is reduced from:
- A. 46 to 23
- B. 46 to 33
- C. 28 to 14
- D. 24 to 12
Correct answer: A
Rationale: The correct answer is A: "46 to 23." In meiosis, the chromosome number is reduced by half to form gametes for sexual reproduction. In humans, where the diploid chromosome number is 46, meiosis results in haploid cells with 23 chromosomes. Choices B, C, and D are incorrect because they do not represent the correct reduction in chromosome number during meiosis.
2. Which organelle is responsible for the synthesis of lipids and steroid hormones?
- A. Rough endoplasmic reticulum
- B. Smooth endoplasmic reticulum
- C. Golgi apparatus
- D. Ribosomes
Correct answer: B
Rationale: The smooth endoplasmic reticulum is the correct organelle responsible for the synthesis of lipids, including phospholipids, cholesterol, and steroid hormones. The rough endoplasmic reticulum is primarily involved in protein synthesis and processing, making choice A incorrect. The Golgi apparatus is responsible for modifying, sorting, and packaging proteins and lipids for transportation, so it is not directly involved in lipid and steroid hormone synthesis, making choice C incorrect. Ribosomes are responsible for protein synthesis and are not involved in lipid or steroid hormone synthesis, making choice D incorrect.
3. Which of the following is often referred to as the powerhouse of the cell?
- A. Nucleus
- B. Chromatin
- C. Mitochondria
- D. Ribosomes
Correct answer: C
Rationale: Mitochondria are known as the powerhouse of the cell because they generate most of the cell's supply of ATP, which is the energy currency used for various cellular processes. The nucleus (Choice A) is the control center of the cell, housing genetic material. Chromatin (Choice B) is a complex of DNA and proteins within the nucleus. Ribosomes (Choice D) are responsible for protein synthesis and not the primary energy production in the cell.
4. Which of the following statements is most accurate regarding the transcription of DNA?
- A. RNA uses reverse transcriptase to make mRNA
- B. DNA uses mRNA to produce tRNA
- C. RNA creates a duplicate copy of DNA
- D. RNA copies DNA to produce mRNA
Correct answer: D
Rationale: The correct answer is D. During transcription, RNA copies DNA to produce mRNA, which carries the genetic information from DNA to the ribosomes for protein synthesis. Choice A is incorrect because reverse transcriptase is not involved in the transcription of DNA. Choice B is incorrect as DNA does not use mRNA to produce tRNA; tRNA is produced through a different process. Choice C is incorrect as RNA does not create a duplicate copy of DNA during transcription; it synthesizes mRNA by copying the DNA template.
5. Which of the following best describes phenotype?
- A. The hereditary potentials and limitations of an individual
- B. The genetic makeup of an individual organism
- C. The entire complex of genes inherited from both parents
- D. All the observable characteristics of an organism
Correct answer: D
Rationale: The correct answer is D: 'All the observable characteristics of an organism.' Phenotype refers to all the observable characteristics of an organism, such as physical appearance, behavior, and other traits, which result from the interaction of its genotype with the environment. Choice A is incorrect because it describes genotype. Choice B is incorrect as it defines genotype, not phenotype. Choice C is incorrect as it refers to the genotype, the genetic information inherited from both parents, rather than the observable traits.
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