Smack' is a drug obtained from the:

Correct Answer: A

Rationale: The correct answer is A. Smack is a street name for heroin, which is derived from the latex of Papaver somniferum, commonly known as the opium poppy. The latex of this plant contains morphine and codeine, which are the main components of heroin. Cannabis sativa (B) refers to marijuana, not smack. Dhatura (C) and Erythroxylum coca (D) are sources of other drugs like scopolamine and cocaine, respectively, not heroin. Therefore, A is the correct answer as it corresponds to the actual source of smack/heroin.

Correct Answer: D

Rationale: The correct answer is D because corticosteroids are known to suppress the immune system by inhibiting the production of pro-inflammatory cytokines and preventing the activation of immune cells. This suppression can lead to a decreased immune response, making it less likely for the patient to exhibit typical signs of immune dysfunction. A: The arthritis masking the immune response is not a plausible explanation as arthritis does not directly affect immune function. B: Corticosteroids do not cause the thymus gland to malfunction; they mainly impact immune response at the cellular level. C: Arthritis affecting immunoglobulin function is not a common mechanism of immune dysfunction in this context.

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.