all humans have how many pairs of chromosomes
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HESI A2

HESI A2 Biology Practice Test 2024

1. How many pairs of chromosomes do all humans have?

Correct answer: B

Rationale: All humans have 23 pairs of chromosomes, totaling 46 chromosomes. Choice A is incorrect because humans do not have 24 pairs. Choice C is incorrect as humans have 23 pairs, not 22 pairs. Choice D is incorrect as humans have 23 pairs of chromosomes, not 20 pairs.

2. A pencil measures 8cm long. What is this in mm?

Correct answer: A

Rationale: To convert centimeters to millimeters, you need to multiply by 10 since 1 centimeter is equal to 10 millimeters. Therefore, 8 cm x 10 mm/cm = 80 mm. The pencil measures 8 cm, which is equivalent to 80 mm when converted. Choice A is correct as it correctly converts 8 cm to mm by multiplying it by 10. Choices B, C, and D are incorrect because they do not apply the correct conversion factor.

3. Which of the following bases is not present in RNA?

Correct answer: B

Rationale: Thymine is not present in RNA. RNA uses uracil as one of its bases, which pairs with adenine. In RNA, adenine does not pair with thymine as in DNA. Cytosine and guanine are the other two bases found in both RNA and DNA.

4. When plants do not receive enough water, their photosynthetic rate drops. This is because:

Correct answer: A

Rationale: When plants do not receive enough water, their photosynthetic rate drops because water is a raw material required for the light reactions in photosynthesis. In the light reactions, water is split to provide electrons, which are then utilized to produce energy carriers used in converting carbon dioxide into glucose during the Calvin cycle. Therefore, without sufficient water, the light reactions cannot proceed effectively, ultimately leading to a decrease in photosynthetic rate. Choice B is incorrect because carbon dioxide is a separate raw material needed for the Calvin cycle, not the light reactions. Choice C is incorrect as water provides electrons, not carbon atoms, for photosynthesis. Choice D is incorrect because fermentation is not directly related to photosynthesis; oxygen is produced during photosynthesis, not fermentation.

5. Why does cellular respiration happen?

Correct answer: C

Rationale: Cellular respiration is the process through which cells break down nutrients such as glucose to produce ATP (adenosine triphosphate), the energy currency of the cell. This process allows cells to extract energy from food molecules and use it for various cellular activities and functions. Choices A, B, and D are incorrect because cellular respiration is specifically about converting nutrients to energy, not about DNA copying, breathing, or cell division.

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