HESI A2
HESI A2 Biology 2024
1. How many pairs of homologous chromosomes do humans have?
- A. 13
- B. 23
- C. 26
- D. 46
Correct answer: D
Rationale: The correct answer is D: 46. Humans have 23 pairs of chromosomes, which include 22 pairs of autosomes and 1 pair of sex chromosomes. Homologous chromosomes are pairs of chromosomes that contain the same genes, one from each parent. Therefore, humans have a total of 46 chromosomes, with 23 pairs of homologous chromosomes. Choices A, B, and C are incorrect as they do not represent the total number of chromosomes in humans or the number of pairs of homologous chromosomes.
2. What is the term for the breakdown of glycogen into glucose subunits?
- A. Hydrolysis
- B. Reduction
- C. Metabolism
- D. Transpiration
Correct answer: A
Rationale: Hydrolysis is the term used to describe the breakdown of large molecules into smaller units by adding water. In the case of glycogen being broken down into glucose subunits, this process involves the addition of water molecules to break the glycosidic bonds between glucose molecules, resulting in the release of individual glucose subunits. This process is crucial for providing cells with a source of energy when needed. Choice B, Reduction, refers to a chemical reaction involving a gain of electrons or a decrease in oxidation state, not the breakdown of glycogen into glucose subunits. Choice C, Metabolism, is a broad term encompassing all biochemical processes in an organism, including anabolism and catabolism, but does not specifically describe the breakdown of glycogen into glucose subunits. Choice D, Transpiration, is the process of water movement through a plant and is not related to the breakdown of glycogen into glucose subunits.
3. What type of cells are involved in meiosis (sex cells)?
- A. Somatic Cells
- B. Gametes
- C. Zygote
- D. Diploid Cells
Correct answer: B
Rationale: The correct answer is B, Gametes. Gametes are the specialized sex cells involved in meiosis, such as sperm and eggs. Somatic cells (A) are non-reproductive cells found in the body, not involved in meiosis. Zygote (C) is the result of fertilization, formed when gametes unite. Diploid cells (D) have two sets of chromosomes, but in meiosis, gametes are produced through a process of cell division that reduces the chromosome number by half to haploid.
4. In an example of a male with hemophilia and a female carrier, what percentage of the offspring is predicted to be carriers only?
- A. 0%
- B. 25%
- C. 50%
- D. 100%
Correct answer: C
Rationale: In this scenario, the male offspring will inherit the X chromosome with the hemophilia gene from the mother, as males have one X chromosome inherited from their mother. The female offspring will inherit one normal X chromosome from the father and one X chromosome with the hemophilia gene from the mother, making them carriers of the hemophilia trait. Therefore, 50% of the offspring will be carriers only. Option A (0%) is incorrect as female offspring will inherit the X chromosome with the hemophilia gene from the mother. Option B (25%) is incorrect as the female offspring will not be unaffected. Option D (100%) is incorrect as not all offspring will be carriers, only the female offspring.
5. Which system maintains the body's balance through the release of hormones directly into the bloodstream?
- A. The gastrointestinal system
- B. The endocrine system
- C. The digestive system
- D. The endocrine system
Correct answer: D
Rationale: The correct answer is D: The endocrine system. The endocrine system maintains the body's balance through the release of hormones directly into the bloodstream. Hormones produced by glands in the endocrine system regulate various bodily functions such as metabolism, growth, and reproduction. This system plays a crucial role in maintaining homeostasis by releasing hormones that help control and coordinate different processes in the body. Choices A, C, and B are incorrect. The gastrointestinal system is responsible for digestion, absorption of nutrients, and excretion of waste; the digestive system includes the gastrointestinal system and other accessory organs; and choice B is a duplicate of the correct answer.
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