Nokea
What is the role of RNA interference in silencing genes?
- A. Increases protein production
- B. Promotes gene mutation
- C. Inhibits the expression of specific genes
- D. Repairs damaged DNA
Correct Answer: C
Rationale: RNA interference (RNAi) is a biological process that involves the silencing of gene expression by inhibiting the translation of mRNA or by degrading mRNA molecules. This mechanism plays a crucial role in regulating gene expression and can be used to selectively silence specific genes. By interfering with the expression of specific genes, RNAi can downregulate protein production from those genes. Therefore, option C, 'Inhibits the expression of specific genes,' is the correct role of RNA interference in silencing genes. Options A, B, and D are incorrect because RNA interference does not increase protein production, promote gene mutation, or repair damaged DNA; its primary function is to inhibit gene expression by degrading or interfering with mRNA.
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Which of the following is a strong acid?
- A. Acetic acid (CH₃COOH)
- B. Hydrochloric acid (HCl)
- C. Citric acid
- D. Carbonic acid (H₂CO₃)
Correct Answer: B
Rationale: Hydrochloric acid (HCl) is a strong acid because it completely ionizes in water to produce hydrogen ions, leading to a high concentration of H⺠ions in solution. This characteristic makes it a strong acid. Acetic acid (CH₃COOH), citric acid, and carbonic acid (H₂CO₃) are weak acids as they only partially ionize in water, resulting in a lower concentration of H⺠ions compared to strong acids. Therefore, hydrochloric acid is the correct choice as a strong acid.
In the cardiovascular system, what does the term 'double circulation' refer to?
- A. The separation of oxygenated and deoxygenated blood flow within the heart.
- B. The regulation of blood pressure through vasoconstriction and vasodilation.
- C. The cyclic contraction and relaxation of the heart muscle.
- D. The existence of two separate circulatory pathways, one for the lungs and one for the body.
Correct Answer: D
Rationale: The term 'double circulation' in the cardiovascular system refers to the existence of two separate circulatory pathways, one for the lungs (pulmonary circulation) and one for the body (systemic circulation). Oxygen-poor blood is pumped from the heart to the lungs for oxygenation, and then oxygen-rich blood is pumped from the lungs back to the heart to be circulated to the rest of the body. Choices A, B, and C are incorrect as they do not accurately describe the concept of 'double circulation.' Choice A refers to the separation of oxygenated and deoxygenated blood within the heart, choice B relates to blood pressure regulation mechanisms, and choice C describes the cardiac muscle's contraction and relaxation, none of which define 'double circulation' in the context of the cardiovascular system.
Alpha waves, characteristic of quiet wakefulness and relaxation, have a frequency range of:
- A. 0.5-4 Hz
- B. 4-8 Hz
- C. 8-13 Hz
- D. 13-30 Hz
Correct Answer: C
Rationale: Alpha waves are neural oscillations in the frequency range of 8-13 Hz, which are typically associated with a state of quiet wakefulness and relaxation. Option C, 8-13 Hz, is the correct frequency range for alpha waves. Choices A, B, and D are incorrect as they do not fall within the specific frequency range characteristic of alpha waves.
Which of the following substances is an example of an acidic gas?
- A. Nitrogen (Nâ‚‚)
- B. Carbon dioxide (COâ‚‚)
- C. Sulfur dioxide (SOâ‚‚)
- D. Oxygen (Oâ‚‚)
Correct Answer: C
Rationale: The correct answer is C, Sulfur dioxide (SOâ‚‚). Sulfur dioxide is an acidic gas because when dissolved in water, it forms sulfurous acid, which imparts acidic properties. Nitrogen (Nâ‚‚), carbon dioxide (COâ‚‚), and oxygen (Oâ‚‚) are not considered acidic gases. Nitrogen is a neutral gas, carbon dioxide forms a weakly acidic solution when dissolved in water, and oxygen is a neutral gas.
How much sugar is in a 1 M solution of sugar water?
- A. 1 L of water
- B. 100 mL of solution
- C. Every 100 g of water
- D. It depends on the type of sugar
Correct Answer: B
Rationale: A 1 M solution of sugar water contains 1 mole of sugar in 1 liter of solution. Since 1 M (molar) solution means there is 1 mole of solute (sugar) dissolved in 1 liter of solvent (water), the correct answer is 100 mL of solution. Choice A, '1 L of water,' is incorrect because it does not specify the total volume of the solution. Choice C, 'Every 100 g of water,' is incorrect as it focuses on the weight of water, not the volume of the solution. Choice D, 'It depends on the type of sugar,' is incorrect since the concentration of a 1 M solution is standardized and does not vary based on the type of sugar used.