HESI A2
Biology HESI A2 Practice Exam
1. Which of the following are found both in open and closed circulatory systems?
- A. Arteries
- B. Red blood cells
- C. Capillaries
- D. Immune cells
Correct answer: C
Rationale: The correct answer is C, Capillaries. Capillaries are found in both open and closed circulatory systems. Capillaries are small blood vessels that connect arteries and veins, allowing for the exchange of nutrients and wastes between the blood and tissues. They are essential components of circulatory systems regardless of whether they are open or closed. Arteries (Choice A) are not found in open circulatory systems, as these systems lack distinct arteries and veins. Red blood cells (Choice B) are present in the blood but are not exclusive to either open or closed circulatory systems. Immune cells (Choice D) are not specific components of circulatory systems, as they are part of the immune system.
2. 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.
3. What is the role of ribosomes in the cell?
- A. Break down cellular waste
- B. Organize cellular division
- C. Synthesize proteins
- D. Provide cellular structure
Correct answer: C
Rationale: The correct answer is C: Synthesize proteins. Ribosomes are responsible for protein synthesis by linking amino acids together. Choice A is incorrect because ribosomes do not break down cellular waste. Choice B is incorrect as ribosomes do not organize cellular division. Choice D is incorrect because ribosomes do not provide cellular structure.
4. Huntington’s disease is carried on the dominant allele. In a situation where two heterozygous parents have the disease, what percentage of their offspring are predicted to be disease-free?
- A. 0%
- B. 25%
- C. 50%
- D. 100%
Correct answer: B
Rationale: In this scenario, both parents are heterozygous for Huntington's disease, meaning each carries one dominant allele (representing the disease) and one recessive allele (representing no disease). When they have offspring, there is a 25% chance that each child will inherit two recessive alleles, making them disease-free. The Punnett square for two heterozygous parents (Hh x Hh) yields a 25% probability of offspring being homozygous recessive (hh) and therefore disease-free. Choice A (0%) is incorrect because there is a possibility of disease-free offspring. Choice C (50%) is incorrect as it represents the likelihood of being a carrier. Choice D (100%) is incorrect as all offspring will not be disease-free in this scenario.
5. In order, from lower to upper, the layers of the atmosphere are:
- A. Exosphere, thermosphere, mesosphere, stratosphere, troposphere
- B. Troposphere, stratosphere, mesosphere, thermosphere, exosphere
- C. Mesosphere, troposphere, stratosphere, thermosphere, exosphere
- D. Thermosphere, troposphere, stratosphere, mesosphere, exosphere
Correct answer: B
Rationale: The correct order of the layers of the atmosphere, from lower to upper, is troposphere, stratosphere, mesosphere, thermosphere, exosphere. The troposphere is the lowest layer where weather phenomena occur. The stratosphere contains the ozone layer, which absorbs and scatters the solar ultraviolet radiation. The mesosphere is where most meteorites burn up upon entering the Earth's atmosphere. The thermosphere is characterized by high temperatures due to the absorption of solar radiation. The exosphere is the outermost layer where the atmosphere transitions into space. Therefore, option B is the correct sequence, as it reflects the ascending order of the Earth's atmospheric layers.
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