HESI RN
Biology Practice Test
1. Which of the following terms is used to represent two alleles that are the same type?
- A. Homosynchronous
 - B. Hypersynchronous
 - C. Heterozygous
 - D. Homozygous
 
Correct answer: D
Rationale: The correct answer is D, 'Homozygous.' Homozygous refers to having two identical alleles for a particular gene. In this context, 'Homosynchronous' (choice A) is not a recognized genetic term. 'Hypersynchronous' (choice B) is not a term used in genetics. 'Heterozygous' (choice C) refers to having two different alleles for a particular gene, which is the opposite of homozygous.
2. Which of the following statements is true if a molecule exhibits adhesion?
- A. Two molecules of the same substance have the ability to stay bonded to one another
 - B. The molecule has the ability to bond to or attract other molecules
 - C. A molecule has the ability to increase its heat when necessary
 - D. The molecule has the ability to form hydrogen bonds
 
Correct answer: B
Rationale: The correct statement is that if a molecule exhibits adhesion, it has the ability to bond to or attract other molecules. Adhesion refers to the ability of a molecule to bind to or attract different types of molecules. Choice A is incorrect because adhesion is about bonding to different molecules, not the same substance. Choice C is incorrect as adhesion does not relate to the ability of a molecule to increase its heat. Choice D is incorrect because forming hydrogen bonds is a specific type of interaction and not a general characteristic of molecules exhibiting adhesion.
3. At the beginning of meiosis, how many chromosomes does the diploid parent cell have?
- A. 23
 - B. 24
 - C. 46
 - D. 54
 
Correct answer: C
Rationale: The correct answer is C: 46. At the start of meiosis, the diploid parent cell contains 46 chromosomes. During meiosis, the number of chromosomes is halved, resulting in each gamete having 23 chromosomes. Choice A (23) is incorrect because that is the number of chromosomes in a human gamete, not the parent cell. Choice B (24) and Choice D (54) are also incorrect as they do not reflect the correct number of chromosomes in a diploid parent cell at the beginning of meiosis.
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. What is the difference between DNA and RNA?
- A. RNA has an extra Phosphate group
 - B. DNA has one less oxygen than RNA
 - C. RNA has one less oxygen than DNA
 - D. DNA has an extra sugar molecule
 
Correct answer: B
Rationale: The correct answer is B. DNA has one less oxygen atom in its sugar molecule (deoxyribose) compared to RNA, which has a ribose sugar. Choice A is incorrect because RNA does not have an extra phosphate group. Choice C is incorrect as RNA actually has one more oxygen atom than DNA. Choice D is incorrect as DNA and RNA have different sugar molecules, with DNA having deoxyribose and RNA having ribose.
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