Nursing Elites

1. The neutral theory of molecular evolution proposes that:

• A. Most mutations in DNA are selectively neutral and do not affect an organism's fitness.
• B. All mutations are beneficial and contribute to the adaptation of a population.
• C. The rate of evolution is primarily driven by strong directional selection pressures.
• D. Genetic drift plays a negligible role in shaping genetic variation within populations.

Correct answer: A

Rationale: Rationale: A) The neutral theory of molecular evolution, proposed by Motoo Kimura in the 1960s, suggests that the majority of mutations that occur in DNA are selectively neutral, meaning they do not have a significant impact on an organism's fitness. These neutral mutations are not subject to natural selection and are allowed to accumulate in populations over time. This theory helps explain the high levels of genetic variation observed within populations. B) Option B is incorrect because not all mutations are beneficial. Mutations can be neutral, harmful, or beneficial, and the neutral theory specifically focuses on the idea that many mutations are neutral in their effects. C) Option C is incorrect because the neutral theory suggests that evolution is not primarily driven by strong directional selection pressures. Instead, it emphasizes the role of genetic drift and the accumulation of neutral mutations in shaping genetic variation. D) Option D is incorrect because

2. What happens to the density of a gas when its temperature increases at constant pressure?

• A. It increases.
• B. It decreases.
• C. It remains the same.
• D. Information is insufficient.

Correct answer: B

Rationale: When the temperature of a gas increases at constant pressure, the average kinetic energy of the gas molecules increases. This leads to the gas molecules moving faster and spreading out more, which causes them to occupy a larger volume. As a result, the density of the gas decreases because the same number of gas molecules are now distributed over a larger space. Choice A is incorrect because as the gas molecules spread out, the density decreases. Choice C is incorrect because the increase in temperature leads to a decrease in density due to the increased volume occupied by the gas molecules. Choice D is incorrect because with the provided scenario of temperature increase at constant pressure, the effect on density can be determined.

3. A 10 kg box rests on a frictionless surface. A horizontal force of 20 N is applied to the box. What is the box's acceleration?

• A. 0.5 m/s²
• B. 1 m/s²
• C. 2 m/s²
• D. 10 m/s²

Correct answer: B

Rationale: The acceleration of an object is given by the formula \(a = \frac{F}{m}\), where \(F\) is the net force acting on the object and \(m\) is the mass of the object. In this case, the net force acting on the box is 20 N, and the mass of the box is 10 kg. Plugging these values into the formula, we get \(a = \frac{20}{10} = 2\) m/s².

4. A ball is thrown horizontally off a cliff. Which of the following forces is responsible for its downward motion?

• A. The force of throwing
• B. Normal force from the air
• C. Tension force from the string (if used)
• D. Gravitational force

Correct answer: D

Rationale: The gravitational force is responsible for the downward motion of the ball. When the ball is thrown horizontally off a cliff, the only force acting on it in the vertical direction is the force of gravity, which pulls the ball downward towards the ground. The other forces mentioned (force of throwing, normal force from the air, tension force from the string) do not contribute to the ball's downward motion in this scenario. The force of throwing initiates the horizontal motion, the normal force from the air opposes the ball's motion through air resistance, and tension force from the string would only be relevant if a string were attached to the ball. Therefore, gravitational force is the primary force responsible for the ball's downward motion in this situation.

5. Which of the following enzymes is responsible for adding a nucleotide to a growing DNA chain?

• A. Helicase
• B. Ligase
• C. Nuclease
• D. Polymerase

Correct answer: D

Rationale: The correct answer is Polymerase. Polymerase is the enzyme responsible for adding nucleotides to a growing DNA chain during DNA replication. Helicase unwinds the DNA double helix to separate the DNA strands for replication, Ligase joins DNA fragments together by catalyzing the formation of phosphodiester bonds between them, and Nuclease cuts or degrades DNA strands. Therefore, choices A, B, and C are incorrect in the context of adding nucleotides to a growing DNA chain.

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