The nurse is caring for a patient being tested for rheumatoid arthritis. In reviewing laboratory values, which should the nurse recognize as being diagnostic of rheumatoid arthritis?

Correct Answer: A

Rationale: The correct answer is A because an elevated C-reactive protein level indicates inflammation, which is a key feature of rheumatoid arthritis. Rheumatoid factor (choice B) is positive in only 70-80% of patients with rheumatoid arthritis, so a negative result does not rule out the disease. White blood cell count (choice C) and antinuclear antibody test (choice D) are not specific to rheumatoid arthritis. In summary, an elevated C-reactive protein level is a more reliable indicator of the disease compared to the other options provided.

Correct Answer: C

Rationale: The correct answer is C: Archaea. Archaea are thought to be the oldest living organisms due to their unique characteristics and genetic similarities to the earliest forms of life. They are known for thriving in extreme environments, resembling conditions on early Earth. Other choices are incorrect because eukaryotes are more complex and evolved later, heterotrophic prokaryotes came after autotrophic prokaryotes, and viruses are not considered living organisms.

Correct Answer: B

Rationale: Rolling circle replication is a mechanism commonly observed in DNA transfer during bacterial conjugation. The process involves the transfer of a single strand of DNA that acts as a template for the synthesis of a complementary strand in the recipient cell. This results in the formation of a circular DNA molecule in the recipient cell. This mechanism is distinct from the semiconservative replication seen in prokaryotic cell division (Choice A), the cell division process of mitosis (Choice C), and the reduction division of meiosis (Choice D). Rolling circle replication is specific to the transfer of genetic material between bacterial cells during conjugation, making Choice B the correct answer.

Correct Answer: D

Rationale: The correct answer is D because extrachromosomal DNA, such as plasmids, can be present in eukaryotic microorganisms. This is true for certain organisms like yeast and some fungi. These DNA molecules are separate from the main chromosomal DNA and can carry additional genetic information. A: mRNA in eukaryotic microorganisms is not short-lived; it can have varying lifespans depending on the specific mRNA molecule and cellular conditions. B: Eukaryotic microorganisms typically have multiple linear chromosomes, not a single circular chromosome. C: While 5s, 16s, and 23s ribosomal RNAs are present in prokaryotic organisms, eukaryotic microorganisms have different types of ribosomal RNA subunits.

Correct Answer: B

Rationale: The correct answer is B: Helper T cells. HIV preferentially infects Helper T cells because they express the CD4 receptor, which serves as the primary binding site for the virus. Once infected, HIV impairs the Helper T cells' function, leading to immune system dysfunction. Memory cells (A), Cytotoxic T cells (C), and Natural killer cells (D) are not the primary targets of HIV infection as they do not express the CD4 receptor necessary for HIV entry and replication. Helper T cells are crucial for orchestrating immune responses, making them the primary target for HIV infection.