Superoxide dismutase is an enzyme that catalyzes the conversion of oxygen radicals to peroxides. Which groups of organisms do not have this enzyme?

Correct Answer: D

Rationale: The correct answer is D: oxylabile anaerobes. These organisms cannot survive in the presence of oxygen and are sensitive to oxygen radicals. Superoxide dismutase is essential for organisms that are exposed to oxygen, as it helps convert harmful oxygen radicals into less harmful peroxides. Therefore, organisms that lack this enzyme, like oxylabile anaerobes, would not be able to detoxify oxygen radicals and would not survive in aerobic environments. A: Aerobes have superoxide dismutase to protect against oxygen radicals. B: Facultative anaerobes can switch between aerobic and anaerobic metabolism and would benefit from having superoxide dismutase. C: Oxyduric anaerobes are resistant to oxygen and can still benefit from superoxide dismutase for detoxification.

Correct Answer: A

Rationale: Rationale: A: Emphysema is characterized by the destruction of alveolar walls and loss of elasticity of the lungs, leading to air trapping and difficulty exhaling. This results in reduced gas exchange and airflow limitation. B: Bronchospasms are more commonly associated with conditions like asthma, not emphysema. C: Abnormal growth of epithelial cells is seen in conditions like lung cancer, not emphysema. D: Excessive mucus production is characteristic of conditions like chronic bronchitis, not emphysema. Summary: The correct answer is A because emphysema specifically involves the loss of elasticity of the lungs due to destruction of alveoli, leading to impaired airflow. Choices B, C, and D are incorrect as they describe features more indicative of other respiratory conditions.

Correct Answer: A

Rationale: The correct answer is A because a codon is a triplet of nucleotides in mRNA that corresponds to a specific amino acid during protein synthesis. To be a codon, the triplet must be in the same reading frame as the start codon (AUG) to maintain the correct reading of the genetic code. Choice B is incorrect because codons are typically consecutive in mRNA. Choice C is incorrect as tRNA sequences are not codons. Choice D is incorrect because all codons correspond to specific amino acids.

Correct Answer: D

Rationale: The correct answer is D: Recombinant DNA. Recombinant DNA refers to the DNA molecule formed by combining DNA from different sources. In genetic engineering, this is created by inserting a foreign DNA fragment into a vector DNA, resulting in a new DNA molecule. Plasmid DNA (A) is a small, circular DNA found in bacteria. Vector DNA (B) is a carrier molecule used to transport foreign DNA into a host cell. Insert DNA (C) is the DNA fragment that is inserted into a vector. Therefore, choice D is the correct answer as it specifically refers to the combined DNA molecule formed in genetic engineering.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.