Biology HESI A2 2024

Correct Answer: B

Rationale: To determine the percentage of offspring that are carriers but not manifesting the disease, we need to consider the Punnett square. When both parents carry the recessive gene, there is a 25% chance of producing homozygous recessive offspring with cystic fibrosis. This means the remaining 75% will be carriers (heterozygous) but not show symptoms. Therefore, the correct answer is B (25%). A: 0% - Incorrect, as carriers are present. C: 50% - Incorrect, as it does not account for the probability of being a carrier. D: 100% - Incorrect, as not all offspring will manifest the disease.

Correct Answer: D

Rationale: The correct answer is D: genus; species. "Felis" is the genus and "catus" is the species in the scientific name Felis catus. Genus is a broader classification that includes closely related species, while species is the most specific classification level. Kingdom (choice A) is too broad, family (choice A) is at a higher level than species, order (choice B) is too specific, subspecies (choice B) is not part of the scientific name, phylum (choice C) is too broad, and class (choice C) is a higher classification level than species.

Correct Answer: B

Rationale: The correct answer is B because it involves a controlled experiment with two distinct groups - one exposed to chocolate and the other not. This allows for comparison to determine the impact of chocolate consumption on acne. Option A lacks a control group for comparison. Option C only uses one participant, which is not enough to draw generalizable conclusions. Option D does not have a control group and the order of exposure is reversed, which may affect the results. In summary, choice B is the most appropriate as it includes a control group, clear exposure to the variable of interest, and enables comparison between the two groups.

Correct Answer: D

Rationale: Correct Answer: D - DNA cannot be altered. Rationale: 1. DNA can be altered through mutations, recombination, and other genetic processes. 2. DNA repair mechanisms exist to correct alterations. 3. Alterations in DNA are essential for evolution and genetic diversity. Summary: A: True - RNA is single-stranded. B: True - RNA contains uracil. C: True - DNA codes for proteins.

Correct Answer: C

Rationale: The correct answer is C: Nitrification. The water cycle includes evaporation, condensation, precipitation, and collection. Nitrification is a process in the nitrogen cycle, not the water cycle. Condensation is the conversion of water vapor into liquid water. Transpiration is the release of water vapor from plants. Absorption refers to water being taken up by plants or soil. Nitrification, the process of converting ammonia into nitrates, is unrelated to the movement of water in the water cycle.