HESI RN
Biology Practice Test
1. A water molecule contains two types of atoms that are covalently bonded. Which of the following makes up a water molecule?
- A. One hydrogen atom and one oxygen atom
- B. One hydrogen atom and two oxygen atoms
- C. Two hydrogen atoms and two oxygen atoms
- D. Two hydrogen atoms and one oxygen atom
Correct answer: D
Rationale: The correct answer is D: Two hydrogen atoms and one oxygen atom. A water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom. This forms a stable structure known as H2O. Choice A is incorrect as water molecule contains two hydrogen atoms. Choices B and C are incorrect as they do not reflect the correct composition of a water molecule.
2. 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).
3. In the hierarchical organizational system, which of these is the most restrictive category?
- A. Genus
- B. Class
- C. Kingdom
- D. Species
Correct answer: D
Rationale: In the biological classification hierarchy, species is the most specific level, defining individual organisms that can interbreed. While genus, class, and kingdom are also categories in the hierarchy, they are broader and encompass a wider range of organisms compared to species. Genus groups together similar species, class groups similar orders, and kingdom is the broadest category grouping together similar phyla.
4. What is considered the main objective of the translation stage of protein synthesis?
- A. To produce amino acids
- B. To produce nucleotides
- C. To produce fatty acids
- D. To produce nucleic acids
Correct answer: A
Rationale: The correct answer is A: To produce amino acids. During the translation stage of protein synthesis, the mRNA is decoded to assemble a specific sequence of amino acids. These amino acids then fold into a functional protein. Choices B, C, and D are incorrect because the translation stage specifically deals with the production of amino acids, not nucleotides, fatty acids, or nucleic acids.
5. The Punnett square shows that one parent carries the recessive gene for a cleft chin (c) while the other parent does not. What percentage of the parents' offspring is predicted to have a cleft chin?
- A. 25%
- B. 50%
- C. 0%
- D. 75%
Correct answer: C
Rationale: The correct answer is 0%. If one parent carries the recessive gene for a cleft chin while the other parent does not, none of the offspring will express the recessive phenotype. This is because in order for a child to have a cleft chin, they would need to inherit the recessive gene from both parents. Therefore, although the offspring could be carriers of the gene, none are predicted to have a cleft chin. Choices A, B, and D are incorrect because the presence of the recessive gene in one parent and its absence in the other would not result in any offspring showing the cleft chin trait.
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