Biology HESI A2 Practice Test

Correct Answer: A

Rationale: The correct answer is A: TGAACGT. To find the matching DNA strand, we need to use complementary base pairing rules: A pairs with T, C pairs with G. Given the segment ACTTGCA, its complementary DNA strand would be TGAACTG. Therefore, the correct answer is A. Option B (GACCATG) is incorrect because it does not follow the complementary base pairing rules. Option C (ACTTGCA) is the same as the original segment given, so it is also incorrect. Option D (None of the above) is incorrect as the correct answer is A.

Correct Answer: A

Rationale: The correct answer is A: Atmosphere. The atmosphere is the layer of gases that surrounds a planet. It consists of different layers, including the stratosphere and troposphere mentioned in the other choices. The biosphere refers to the regions on Earth where living organisms exist, not the gases surrounding the planet. Therefore, the correct term for the mixture of gases surrounding a planet is the atmosphere.

Correct Answer: C

Rationale: The correct answer is C (bb) because tan fur is the recessive phenotype controlled by the tan allele (b). Since the black allele (B) exhibits complete dominance, a dog must have two copies of the tan allele (bb) to have a tan fur phenotype. Choice A (BB) and B (Bb) would result in black fur, not tan. Choice D (Not enough information) is incorrect as the question provides enough information to determine the correct genotype based on the phenotype given.

Correct Answer: D

Rationale: The correct answer is D because optical microscopy utilizes visible light (B) to observe samples. This method does not use scanning electrons (A) as in electron microscopy. While some optical microscopes may use dyes (C), it is not a defining characteristic. Therefore, D is correct as it acknowledges both the use of visible light and the potential use of dyes in optical microscopy.

Correct Answer: B

Rationale: The correct answer is B: They lower the activation energy needed. Enzymes lower the activation energy required for a reaction to occur, facilitating the reaction without being consumed in the process. This is crucial in speeding up biological processes. Choices A, C, and D are all true statements about enzymes. A: Enzymes catalyze reactions by speeding up the rate of a chemical reaction. C: Enzymes have an active site where substrate molecules bind, facilitating the reaction. D: Enzymes are typically proteins, although some RNA molecules can also exhibit catalytic activity.