Nokea
Which type of RNA is used to carry genetic code copied from DNA?
- A. mRNA
- B. tRNA
- C. rRNA
- D. None of the above.
Correct Answer: A
Rationale: The correct answer is mRNA. Messenger RNA (mRNA) carries the genetic information copied from DNA in the cell nucleus to the ribosomes in the cytoplasm, where it directs protein synthesis. Transfer RNA (tRNA) brings amino acids to the ribosomes during protein synthesis, while ribosomal RNA (rRNA) is a component of the ribosomes where protein synthesis occurs. Therefore, mRNA is the specific type of RNA that carries the genetic code from DNA.
You may also like to solve these questions
Which type of RNA is used to carry the genetic code copied from DNA?
- A. mRNA
- B. tRNA
- C. rRNA
- D. None of the above
Correct Answer: A
Rationale: The correct answer is mRNA (messenger RNA). mRNA is responsible for carrying the genetic information copied from DNA in the cell nucleus to the ribosomes in the cytoplasm where protein synthesis occurs. This process is known as transcription. mRNA acts as a messenger, delivering the genetic instructions to the ribosomes for protein synthesis. In contrast, tRNA (transfer RNA) brings specific amino acids to the ribosome during translation, helping to assemble the protein chain. rRNA (ribosomal RNA) forms a structural and catalytic part of the ribosome itself, aiding in protein synthesis. Therefore, among the options provided, mRNA is the RNA type directly involved in carrying the genetic code from DNA for protein production.
Will solids always sink in liquids?
- A. True, a solid is hard, and liquids are not.
- B. True, solids are heavier than liquids.
- C. False, solids have a smooth surface so they will float.
- D. False, it depends on the density of the solid and liquid.
Correct Answer: D
Rationale: Solids will not always sink in liquids. Whether a solid sinks or floats in a liquid depends on the relative densities of the solid and the liquid. If the density of the solid is greater than that of the liquid, it will sink. If the density of the solid is less than that of the liquid, it will float. Therefore, it is incorrect to state that solids will always sink in liquids without considering their respective densities. The weight or hardness of the solid and the smoothness of its surface do not determine whether it will sink or float in a liquid. The critical factor is the density relationship between the solid and the liquid.
What products are formed when methane undergoes combustion?
- A. CHâ‚„ and Oâ‚‚
- B. COâ‚‚ and Hâ‚‚O
- C. Both COâ‚‚ and Hâ‚‚O
- D. None of the above
Correct Answer: B
Rationale: When methane (CH₄) undergoes combustion with oxygen (O₂), the products formed are carbon dioxide (CO₂) and water (H₂O). The balanced chemical equation for this reaction is: CH₄ + 2O₂ → CO₂ + 2H₂O. Therefore, the correct answer is option B, CO₂ and H₂O. The combustion of methane is a common example of a hydrocarbon reacting with oxygen to produce carbon dioxide and water, releasing energy in the form of heat and light.
Which of the following statements about dissociation is false?
- A. It is reversible.
- B. Ions are not present.
- C. It involves molecules separating.
- D. None of the above.
Correct Answer: B
Rationale: The correct answer is B - 'Ions are not present.' Dissociation involves the separation of molecules into ions. It is a reversible process where molecules break apart into ions. Choice A is true as dissociation is reversible, and Choice C is accurate as it correctly describes the process of dissociation. Therefore, the false statement is that ions are not present during dissociation.
What is the density of carbon tetrachloride if a flask weighing 345.8 g is filled with 225 mL of the liquid, and the total weight of the flask and liquid is 703.55 g?
- A. 1.59 g/mL
- B. 2.76 g/mL
- C. 1.4 g/mL
- D. None of the above
Correct Answer: A
Rationale: To find the density of carbon tetrachloride, we first need to determine the weight of the liquid only. The weight of the liquid can be calculated by subtracting the weight of the empty flask from the total weight of the flask and liquid: 703.55 g - 345.8 g = 357.75 g. Now, using the volume of the liquid (225 mL) and its weight (357.75 g), we can calculate the density: Density = Mass/Volume = 357.75 g / 225 mL ĉ� 1.59 g/mL. Therefore, the correct answer is A, 1.59 g/mL.