HESI RN
Biology Practice Test
1. Which of the following provides support and shape to the cell?
- A. Microtubules
- B. Microfilaments
- C. Cilia
- D. Microvilli
Correct answer: A
Rationale: Microtubules are fundamental components of the cytoskeleton in a cell, playing a crucial role in providing structural support and maintaining the cell's shape. They are composed of tubulin protein subunits and are involved in various cellular processes like cell division, intracellular transport, and cell motility. Microfilaments, on the other hand, are involved in cell movement and maintaining cell shape but are not primarily responsible for supporting the cell's overall structure. Cilia and microvilli are cellular projections that aid in movement and absorption, respectively, but they do not play a significant role in providing structural support to the cell.
2. What cell structure is responsible for efficiently packaging DNA into a small volume to fit into the nucleus of a cell and protect the DNA structure and sequence?
- A. Golgi apparatus
- B. Chromatin
- C. Smooth endoplasmic reticulum
- D. Mitochondria
Correct answer: B
Rationale: Chromatin is the correct answer. Chromatin is responsible for packaging DNA into a more compact, dense structure to fit into the nucleus and protect the DNA. The Golgi apparatus is involved in processing and packaging proteins, not DNA. Smooth endoplasmic reticulum is involved in lipid metabolism and detoxification. Mitochondria are known as the powerhouse of the cell responsible for energy production, not DNA packaging.
3. The term pleiotropy is best defined as which of the following?
- A. A situation in which one gene remains unexpressed
- B. One gene influencing multiple, seemingly unrelated phenotypic traits
- C. Two genes affected by a single allele
- D. A condition in which multiple genes are missing
Correct answer: B
Rationale: Pleiotropy is best defined as one gene influencing multiple, seemingly unrelated phenotypic traits. This phenomenon showcases the multifunctionality of genes, where a single gene can have effects on various aspects of an organism's phenotype. Choices A, C, and D do not accurately capture the concept of pleiotropy. Option A refers to gene expression, not pleiotropy. Option C describes genetic interactions but not in the context of pleiotropy. Option D talks about missing genes, which is unrelated to the definition of pleiotropy.
4. Which of the following is not one of the four nitrogenous bases that make up the DNA structure?
- A. Adenine
- B. Guanine
- C. Uracil
- D. Thymine
Correct answer: C
Rationale: The correct answer is C: Uracil. Uracil is found in RNA, not DNA. The four nitrogenous bases in DNA are adenine, thymine, cytosine, and guanine. Choice A, Adenine, is a nitrogenous base in DNA. Choice B, Guanine, is another nitrogenous base in DNA. Choice D, Thymine, is also one of the four nitrogenous bases in DNA. Therefore, the correct answer is Uracil (Choice C).
5. Which of the following molecules contains the code required for replication?
- A. Deoxyribonucleic acid (DNA)
- B. Transfer RNA (tRNA)
- C. Messenger RNA (mRNA)
- D. Ribonucleic acid (RNA)
Correct answer: A
Rationale: The correct answer is A: Deoxyribonucleic acid (DNA). DNA contains the genetic information essential for replication, ensuring the accurate transmission of genetic material from one generation to the next. Choice B, Transfer RNA (tRNA), is involved in protein synthesis, not replication. Choice C, Messenger RNA (mRNA), carries genetic information from DNA to the ribosome but does not contain the code for replication. Choice D, Ribonucleic acid (RNA), is a broader category that includes both mRNA and tRNA, but the specific molecule containing the code required for replication is DNA.
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