Why Correct: Reverse transcriptase catalyzes DNA synthesis using an RNA template, a process called reverse transcription that defines retroviruses like HIV.
Distractor Analysis: DNA polymerase replicates DNA from a DNA template during cellular division. RNA polymerase transcribes RNA from a DNA template during gene expression. Endonuclease cleaves nucleic acids internally for editing or repair, not synthesis.
Takeaway: Retroviral reverse transcriptase lacks proofreading ability, leading to high mutation rates that facilitate viral evolution and drug resistance.

Why Correct: Bacteria produce restriction enzymes as a defense mechanism against bacteriophages, cutting foreign DNA at specific recognition sequences while protecting their own DNA through methylation.
Distractor Analysis: Eukaryotic cells lack restriction enzymes entirely, using other immune defenses. Yeast are eukaryotic fungi that don't produce restriction enzymes. 'All cells' is incorrect since only prokaryotic bacteria and archaea synthesize these enzymes.
Takeaway: Restriction enzymes are named using a three-letter code from the bacterial species (like EcoRI from E. coli) followed by a Roman numeral for the specific enzyme.

Why Correct: Insulin was the first hormone produced via genetic engineering, achieved in 1978 by inserting the human insulin gene into E. coli bacteria for commercial production.
Distractor Analysis: Estrogen regulates female reproductive functions and is synthesized in ovaries. Testosterone drives male sexual development and is produced in testes. Thyroxin controls metabolic rate and is secreted by the thyroid gland.
Takeaway: The first genetically engineered drug approved for human use was human insulin (Humulin) in 1982, developed through collaboration between Genentech and Eli Lilly.