The main function of bacterial ribosomes is:

Correct Answer: B

Rationale: The correct answer is B: protein synthesis. Bacterial ribosomes are responsible for translating messenger RNA into proteins through a process called translation. Ribosomes are composed of both protein and RNA molecules and facilitate the binding of transfer RNA to the messenger RNA to assemble the amino acids in the correct order to form a protein. DNA replication (A) is carried out by enzymes such as DNA polymerase, not ribosomes. Cell wall synthesis (C) is a process involving enzymes that build the structure of the cell wall in bacteria. RNA splicing (D) is a eukaryotic process that involves removing introns from pre-mRNA molecules, which is not a function of bacterial ribosomes.

Correct Answer: B

Rationale: The correct answer is B: Corynebacterium diphtheriae. This bacterium produces a toxin that causes diphtheria by inhibiting protein synthesis, leading to the formation of a pseudomembrane in the throat. Bordetella pertussis causes whooping cough, Streptococcus pyogenes causes strep throat, and Neisseria meningitidis causes meningitis. Corynebacterium diphtheriae is the only bacterium among the choices known to cause diphtheria due to its specific toxin production.

Correct Answer: B

Rationale: The correct answer is B: Mycobacterium tuberculosis. This bacterium is responsible for causing tuberculosis. Mycobacterium leprae (choice A) causes leprosy, not tuberculosis. Streptococcus pneumoniae (choice C) is known for causing pneumonia, not tuberculosis. Neisseria gonorrhoeae (choice D) is responsible for causing gonorrhea, not tuberculosis. Mycobacterium tuberculosis is the specific bacterium associated with tuberculosis due to its ability to infect the lungs and other organs, leading to the characteristic symptoms of the disease.

Correct Answer: C

Rationale: Rationale for choice C (Adenovirus) being correct: 1. Adenovirus is a common cause of acute hemorrhagic cystitis. 2. Adenovirus infects the bladder epithelium, leading to inflammation and bleeding. 3. Symptoms include hematuria and bladder pain. 4. Diagnosis is confirmed through viral culture or PCR testing. Summary of why other choices are incorrect: A: Parvovirus B19 - More commonly associated with erythema infectiosum (fifth disease) and aplastic anemia. B: CMV - Known to cause congenital infections, mononucleosis, and retinitis, not typically associated with hemorrhagic cystitis. D: Herpesvirus type 2 - Commonly causes genital herpes, but not typically associated with acute hemorrhagic cystitis.

Correct Answer: C

Rationale: The correct answer is C: (+RNA). This indicates that the scientist found a positive-sense RNA strand that can be directly translated by host cell machinery to produce viral proteins. Positive-sense RNA can act as messenger RNA, allowing immediate protein synthesis during viral replication. Choice A (RNA major) and D (RNA minor) are not standard terms used to describe RNA strands in virology. Choice B (-RNA) indicates a negative-sense RNA strand, which requires transcription to form a complementary positive-sense strand before protein synthesis. Thus, the identification of a strand of RNA that directly codes for viral proteins aligns with the characteristics of a positive-sense RNA strand.