1. History of exposure
   Recent ingestion, inhalation, or skin exposure to pesticide/insecticide, often in farming or pesticide work.
2. Typical cholinergic toxidrome
   • Salivation, sweating, lacrimation
   • Miosis (pinpoint pupils), blurred vision
   • Bronchorrhea/bronchospasm, wheeze, respiratory distress
   • Bradycardia
   • Vomiting, diarrhea, abdominal cramps, urination
   • Muscle fasciculations, weakness, paralysis
   • Confusion, seizures, coma in severe poisoning
3. Laboratory confirmation
   • Low red blood cell acetylcholinesterase (RBC AChE): more specific for significant organophosphate exposure
   • Low plasma pseudocholinesterase (butyrylcholinesterase): supportive but less specific

Diagnosis depends on a history of recent exposure, clinical features of diffuse cholinergic stimulation, and reduced erythrocyte acetylcholinesterase and plasma pseudocholinesterase activity.

1. A. Rf value
   Ratio of distance travelled by solute to distance travelled by solvent front in chromatography.
2. C. HRE (Hormone Response Elements)
   Hormone-receptor complexes bind specific DNA hormone-response elements.
3. D. Hydroxymethylbilane synthase
   Also called porphobilinogen deaminase. Deficient in acute intermittent porphyria.
4. D. Single-stranded binding proteins
   Replication protein A, replication factor C, and PCNA are eukaryotic replication proteins. Generic SSB proteins are classically associated with prokaryotic DNA replication.
5. A. Pribnow box
   The bacterial promoter region at about -10 bp.
6. A. Estimation of cholinesterase
   Organophosphorus poisoning is supported by decreased cholinesterase activity, especially RBC acetylcholinesterase.
7. A. Synthesized by hepatocytes
   Gamma globulins are immunoglobulins, produced by plasma cells derived from B lymphocytes, not hepatocytes.
8. B. DNase I
   DNase I produces single-strand nicks in DNA.
9. D. Cysteine is essential for individuals consuming a diet deficient in methionine
   Cysteine is normally nonessential but becomes conditionally essential when methionine is deficient.
10. B. ALT and AST
    These are markers of hepatocellular injury. ALP and GGT mainly indicate cholestasis.
11. A. Melatonin - Tryptophan
    Tryptophan → serotonin → melatonin.
12. C. Fumarate
    Fumarate produced in the urea cycle enters the TCA cycle through the aspartate-argininosuccinate shunt.
13. D. Dihydrofolate reductase - methotrexate
    Methotrexate inhibits dihydrofolate reductase.

• In the usual nuclear genetic code, UGA is a stop codon.
• In mitochondria, it is reassigned to tryptophan.