HESI A2 Biology 2024

Correct Answer: A

Rationale: The correct answer is A. When messenger RNA reaches the cytoplasm, it attaches to a ribosome for protein synthesis. Ribosomes are the cellular machinery responsible for translating the genetic code carried by mRNA into proteins. Option B is incorrect as mRNA does not "unzip" in the cytoplasm. Option C is incorrect because mRNA does not pair with DNA bases in the cytoplasm; it pairs with ribosomes. Option D is incorrect as mRNA does not "pull free" of the DNA strand in the cytoplasm; it has already been transcribed from DNA in the nucleus.

Correct Answer: B

Rationale: The correct answer is B (50%). Polydactylism is a dominant trait. If both parents have polydactylism, they must be heterozygous (Aa). When they reproduce, the Punnett square shows a 25% chance of AA, 50% chance of Aa, and 25% chance of aa offspring. Thus, 50% of their offspring are predicted to manifest the anomaly. Choice A (25%) is incorrect because that would be the percentage if both parents were homozygous dominant (AA). Choice C (75%) is incorrect because that would be the percentage if both parents were homozygous recessive (aa). Choice D (100%) is incorrect because even though both parents have the trait, they could still be carriers (Aa) and produce offspring without the anomaly.

Correct Answer: A

Rationale: The correct answer is A: Mitochondrion. Mitochondria are known as the powerhouse of the cell due to their role in energy production through cellular respiration. They generate ATP, the main energy currency of the cell, through the citric acid cycle and oxidative phosphorylation. Vacuole (B) stores materials, cell membrane (C) regulates what enters and exits the cell, and ribosome (D) is responsible for protein synthesis. Mitochondria uniquely carry out the process of energy production, making them the correct choice.

Correct Answer: A

Rationale: The correct answer is A: Hydrogen atoms. Saturated fats have all of their carbon atoms bonded to hydrogen atoms, with no double bonds between carbon atoms. This results in a "saturated" molecule with as many hydrogen atoms as possible. Choices B, C, and D are incorrect because saturated fats are not saturated with carbon, oxygen, or nitrogen atoms. These choices do not accurately reflect the chemical structure of saturated fats, which are primarily composed of carbon and hydrogen atoms.

Correct Answer: D

Rationale: The correct answer is D: Decomposer. Decomposers have the greatest energy efficiency among the given choices because they obtain energy by breaking down organic matter into simpler substances. This process requires less energy compared to the consumption and digestion processes in herbivores, carnivores, and omnivores. Decomposers play a vital role in recycling nutrients in ecosystems. Herbivores, carnivores, and omnivores have lower energy efficiency as they need to expend energy in hunting, digesting, and metabolizing food sources.