HESI A2 Biology 2024

Correct Answer: D

Rationale: The correct answer is D (2 females : 1 male) because in this scenario, the male offspring will inherit the X chromosome without the hemophilia gene from the mother. The female offspring will inherit one X chromosome with the hemophilia gene from the carrier mother and one X chromosome without the gene from the father. Therefore, 2 out of 3 offspring are predicted neither to carry nor manifest the disease. Choice A (0 females : 1 male) is incorrect because females can also be carriers of hemophilia. Choice B (1 female : 1 male) is incorrect because it doesn't account for the possibility of female carriers. Choice C (1 female : 0 males) is incorrect because it doesn't consider the transmission of the X chromosome from the mother to the sons.

Correct Answer: B

Rationale: The correct answer is B: Carbohydrates and lipids. Carbohydrates are composed of carbon, hydrogen, and oxygen in a ratio of 1:2:1. Lipids are also made of carbon, hydrogen, and oxygen, but in different ratios. Proteins (choice A and C) contain nitrogen in addition to carbon, hydrogen, and oxygen. Nucleic acids (choice D) contain nitrogen, phosphorus, carbon, hydrogen, and oxygen. Therefore, only carbohydrates and lipids consist of only carbon, hydrogen, and oxygen.

Correct Answer: B

Rationale: During glycolysis, glucose is broken down into molecules of pyruvic acid through a series of enzymatic reactions. This process occurs in the cytoplasm of cells and is the first step in cellular respiration. Pyruvic acid can then enter the citric acid cycle (Kreb's cycle) to further generate ATP. Choice A is incorrect because glucose's energy is not entirely lost but rather partially captured in the form of ATP. Choice C is incorrect as glucose is not stored in NADH but rather NADH is generated during glycolysis. Choice D is incorrect as glucose does not join with molecules of citric acid during glycolysis but rather pyruvic acid is the end product.

Correct Answer: B

Rationale: The correct answer is B: Virus. A virus is a structure composed of a core of nucleic acid (either RNA or DNA) surrounded by a protein coat. This structure allows viruses to infect host cells and replicate. Blue-green algae (option C) are photosynthetic organisms composed of cells with chlorophyll. RNA (option A) is a type of nucleic acid but does not necessarily have a protein coat. Saprophytes (option D) are organisms that obtain nutrients from decaying organic matter and do not typically have a core of nucleic acid surrounded by a protein coat.

Correct Answer: A

Rationale: The correct answer is A because it involves testing the impact of radiation from a single cell phone on the temperature of water in a test tube in a controlled manner. By letting the phone ring for two minutes and recording the temperature before and after, the researcher can isolate the effects of radiation. Choice B introduces additional variables by varying the ringing time, making it difficult to determine the specific impact of radiation. Choice C introduces the factor of different cell phone brands, which may have varying radiation levels and could confound the results. Choice D also introduces multiple variables by using different ringing times and phone brands, making it challenging to attribute any temperature changes solely to radiation from the cell phones. Therefore, choice A is the most appropriate as it ensures a controlled experiment to directly test the hypothesis regarding the impact of cell phone radiation on water temperature.