HESI A2
Biology HESI A2 2024
1. Which statement is untrue?
- A. RNA is single-stranded.
- B. RNA contains uracil.
- C. DNA codes for proteins.
- D. DNA cannot be altered.
Correct answer: D
Rationale: DNA can be altered through various processes such as mutations, genetic engineering, and epigenetic modifications. Changes in DNA can occur naturally or through external influences, leading to variations in the genetic code. Therefore, the statement that DNA cannot be altered is untrue. Choices A, B, and C are true statements. RNA is indeed single-stranded, RNA contains uracil instead of thymine, and DNA serves as a template for protein synthesis.
2. The procedure to focus an image using a compound microscope involves
- A. Adjusting the coarse adjustment each time a new magnification is selected
- B. Adjusting the fine adjustment each time a new magnification is selected
- C. Adjusting the stage each time a new magnification is selected
- D. All of the above
Correct answer: B
Rationale: When using a compound microscope, it is essential to adjust the fine adjustment knob each time you switch to a new magnification level. The fine adjustment knob allows for precise focusing on the specimen at different magnifications, ensuring a clear and sharp image. The coarse adjustment knob is typically used only at the lower magnification settings to bring the image into view roughly. Adjusting the stage may be necessary based on the size and thickness of the specimen, but it does not need to be done every time a new magnification is selected. Therefore, option B is the correct choice as it focuses on the key aspect of precise focusing during magnification changes.
3. Which gives the order of four taxonomic categories from least to most specific?
- A. Kingdom, phylum, class, order
- B. Kingdom, phylum, order, class
- C. Kingdom, order, phylum, class
- D. Kingdom, class, order, phylum
Correct answer: A
Rationale: The correct order of the four taxonomic categories from least to most specific is Kingdom, phylum, class, and order. This sequence adheres to the hierarchical system of classification where organisms are grouped based on shared characteristics, becoming more specific as you move from Kingdom to order. Choice B is incorrect as the order of 'order' and 'class' is swapped. Choice C is incorrect as 'order' precedes 'phylum' instead of following it. Choice D is incorrect as 'class' should come before 'order'.
4. Which organelle organizes protein synthesis?
- A. mitochondrion
- B. nucleus
- C. ribosome
- D. vacuole
Correct answer: C
Rationale: Ribosomes are the organelles responsible for organizing protein synthesis. They are the protein factories of the cell, where amino acids are linked together to form proteins. Mitochondria are known as the powerhouse of the cell, responsible for energy production. The nucleus contains the cell's genetic material but does not directly organize protein synthesis. Vacuoles are responsible for storage and maintaining the cell's turgidity.
5. What is DNA made of?
- A. Proteins
- B. Nucleotides
- C. Lipids
- D. Carbohydrates
Correct answer: B
Rationale: DNA is made up of nucleotides, which are the building blocks of genetic material. Choice A (Proteins) is incorrect because while proteins play a crucial role in the body, they are not the building blocks of DNA. Choice C (Lipids) and Choice D (Carbohydrates) are also incorrect as they are not the primary components of DNA.
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