Some antibiotics work by preventing protein synthesis in bacteria by binding to their ribosomes. Which statement explains why these antibiotics kill bacterial cells but not human cells? A. Antibiotics recognize human genes but not bacterial genes B. Ribosomes in human cells have a different structure to those in bacterial cells C. mRNA in bacterial cells is not processed before translation D. Both DNA and ribosomes are located in the cytoplasm in bacteria E. Ribosome in human cells is located inside the nucleus 9. Shine Dalgarno sequence is A. an RNA component of ribosome B. a promoter sequence C. a sequence for initiator tRNA binding D. located upstream of the coding sequence E. a sequence for recognition by RNA polymerase holoenzyme 10. Which of the following statements about ribosome is INCORRECT? A. Ribosome consists of protein and RNA B. 50S subunit can’t bind to 30S subunit till IF1 an IF3 dissociate from 30S subunit C. Energy is consumed when ribosome moves along the mRNA in elongation D. Releasing factors bind to the A site on the ribosome E. Ribosome moves forward on the mRNA from 3 to 5′ direction Section B: True / False (10 marks) 1. T or F The two sequences shown below are complementary to each other. GTCGAC CAGCUG 2. Tor F 3. Tor F 4. Tor F Telomerase possesses RNA polymerase activity. Topoisomerase binds to DNA ahead of the replication fork. snRNA is not transcribed during translation. Promoter is located in the intron of pre-mRNA. Poly-A tail is added to RNA in bacteria. Translation stops when Stop codon arrives E site in ribosome. 5. Tor F 6. Tor F 7. Tor F 8. EF-G is used in translation termination. Tor F Tor F 9. A subunit of hemoglobin carries more oxygen molecule than a myoglobin does. 10. The formation of carbamate group in hemoglobin reduces its affinity to oxygen. Tor F

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