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Self Assessment Question 1

Self Assessment Question 1. Which of the following statements is true? RNA polymerase has a proofreading activity.      Prokaryotic RNA usually undergoes nuclear processing.      Polypeptides are synthesized by addition of amino acids to the amino terminus.     

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Self Assessment Question 1

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  1. Self Assessment Question 1 • Which of the following statements is true? • RNA polymerase has a proofreading activity.      • Prokaryotic RNA usually undergoes nuclear processing.      • Polypeptides are synthesized by addition of amino acids to the amino terminus.      • The 3' end of mRNA corresponds to the carboxyl terminus of the protein.

  2. Self Assessment Question 1 Answer • Which of the following statements is true? • RNA polymerase has a proofreading activity.      • Prokaryotic RNA usually undergoes nuclear processing.      • Polypeptides are synthesized by addition of amino acids to the amino terminus.      • The 3' end of mRNA corresponds to the carboxyl terminus of the protein.CORRECT ANSWER

  3. Fig. 8.3 DNA is read in 5’ to 3’ direction Protein is made from the amino terminus to carboxyl terminus

  4. Self Assessment Question 2 • Which of the following is true regarding RNA processing? • It involves removal of introns. • It occurs before transcription.      • It is a rare event that only occurs in response to DNA damage.      • It occurs in prokaryotes.      • None of the above

  5. Self Assessment Question 2 Answer • Which of the following is true regarding RNA processing? • It involves removal of introns.CORRECT ANSWER • It occurs before transcription.      • It is a rare event that only occurs in response to DNA damage.      • It occurs in prokaryotes.      • None of the above

  6. mRNA Processing in Eukaryotes: • Important points: • Exons - coding sequences • Introns- non-coding sequences • 5’ end is processed by addition of a 5’methylated cap • 3’ end is processed by cleavage by an endonuclease to yield a 3’ hydroxyl group where adenylic acid residues are added by poly (A) polymerase to give a poly(A) tail (100-250 As) • RNA splicing - introns excised and exonic sequences ligated together WH Freeman, Molecular Cell Biology, 5th Edition, 2004.

  7. Self Assessment Question 3 • Which of the following features is common to both DNA replication and transcription? • Nucleotides are added to the 5' end of the newly synthesized strand.      • A sugar-phosphate bond is formed between the 3' hydroxyl and the 5' phosphate.    • Deoxyribonucleotides are incorporated into the growing sequence.      • Both RNA and DNA polymerases require oligonucleotide priming.

  8. Self Assessment Question 3 Answer • Which of the following features is common to both DNA replication and transcription? • Nucleotides are added to the 5' end of the newly synthesized strand.      • A sugar-phosphate bond is formed between the 3' hydroxyl and the 5' phosphate.CORRECT ANSWER • Deoxyribonucleotides are incorporated into the growing sequence.      • Both RNA and DNA polymerases require oligonucleotide priming.

  9. TRANSCRIPTION: Polymerization of ribonucleotides by RNA polymerase during trancription • Important points: • One strand of DNA acts as the template - determining the order in which ribonucleoside triphosphate monomers (rNTPs) are polymerized to form a complementary RNA chain. • Polymerization reaction is catalyzed by RNA polymerase. • A phosphodiester bond is formed between the 3’ oxygen and the alpha phosphate of the incoming rNTP. • RNA molecules are always synthesized in a 5’ to 3’ direction. WH Freeman, Molecular Cell Biology, 5th Edition, 2004.

  10. Self Assessment Question 4 • The site of RNA polymerase binding to the DNA template is called: • Enhancer      • Domain      • Leader sequences      • Carboxyl end      • Promoter  

  11. Self Assessment Question 4 Answer • The site of RNA polymerase binding to the DNA template is called: • Enhancer      • Domain      • Leader sequences      • Carboxyl end      • PromoterCORRECT ANSWER

  12. TRANSCRIPTION: WH Freeman, Molecular Cell Biology, 5th Edition, 2004.

  13. Self Assessment Question 5 • All of the following may result from promoter mutations, except: • Decreased affinity for RNA polymerase      • Increased affinity for RNA polymerase      • Mutant RNA polymerase • Unregulated transcription      • A new phenotype

  14. Self Assessment Question 5 Answer • All of the following may result from promoter mutations, except: • Decreased affinity for RNA polymerase      • Increased affinity for RNA polymerase      • Mutant RNA polymeraseCORRECT ANSWER • Unregulated transcription      • A new phenotype *Mutant RNA polymerase is not the result of a mutation in a promoter sequence but is the result of a mutation in the actual coding sequence of RNA polymerase.

  15. Self Assessment Question 6 • Introns within primary eukaryotic transcripts: • Are joined to form mature mRNA      • Are highly conserved in nucleotide sequence      • Often function as exons in other genes      • Vary considerably in size and number among different genes

  16. Self Assessment Question 6 Answer • Introns within primary eukaryotic transcripts: • Are joined to form mature mRNA      • Are highly conserved in nucleotide sequence      • Often function as exons in other genes      • Vary considerably in size and number among different genesCORRECT ANSWER

  17. Self Assessment Question 7 • Which of the following statements is true of polypeptide chains and nucleotide chains?   • Both have a sugar-phosphate backbone.      • Both are chains consisting of 20 types of repeating units.      • Both types of polymers are linear and unbranched.    • Both types of molecules contain unambiguous and interconvertible triplet codes.  

  18. Self Assessment Question 7 Answer • Which of the following statements is true of polypeptide chains and nucleotide chains?   • Both have a sugar-phosphate backbone.      • Both are chains consisting of 20 types of repeating units.      • Both types of polymers are linear and unbranched.CORRECT ANSWER • Both types of molecules contain unambiguous and interconvertible triplet codes.  

  19. Self Assessment Question 8 • Which of the following is unique to eukaryotes? • 5' polyadenylation of mRNA      • Polycistronic mRNA      • Coupled transcription-translation      • Removal of introns

  20. Self Assessment Question 8 Answer • Which of the following is unique to eukaryotes? • 5' polyadenylation of mRNA      • Polycistronic mRNA      • Coupled transcription-translation      • Removal of intronsCORRECT ANSWER

  21. Self Assessment Question 9 • Which of the following is unique to prokaryotes? • Coupled transcription-translation • Removal of introns      • 3' polyadenylation      • mRNA capping      • Promoter sequences

  22. Self Assessment Question 9 Answer • Which of the following is unique to prokaryotes? • Coupled transcription-translationCORRECT ANSWER • Removal of introns      • 3' polyadenylation      • mRNA capping      • Promoter sequences

  23. Self Assessment Question 10 • The genetic code is degenerate because: • mRNA is rapidly degraded.      • The code is not universal among organisms.      • Some amino acids have more than one codon. • Frameshift mutations are tolerated.      • Stop codons may have corresponding tRNA molecules.

  24. Self Assessment Question 10 Answer • The genetic code is degenerate because: • mRNA is rapidly degraded.      • The code is not universal among organisms.      • Some amino acids have more than one codon.CORRECT ANSWER • Frameshift mutations are tolerated.      • Stop codons may have corresponding tRNA molecules.

  25. Genetic Code • Most of the codons were determined from in vitropolypeptide synthesis • Genetic code is universal = the same triplet codons specify the same amino acids in all species • Mutations occur when changes in codons alter amino acids in proteins

  26. Self Assessment Question 11 • All of the following are directly involved in translation except: • mRNA      • tRNA      • DNA    • Ribosomes      • Elongation Factor (ELF) proteins  

  27. Self Assessment Question 11 Answer • All of the following are directly involved in translation except: • mRNA      • tRNA      • DNACORRECT ANSWER • Ribosomes      • Elongation Factor (ELF) proteins  

  28. Self Assessment Question 12 • Which of the following is true regarding gene expression? • Only one gene can be present within a given DNA sequence.      • Mistakes in transcription are corrected by RNA polymerase.      • The ribosome binding site lies at the 3' end of mRNA.      • A change in genotype always results in a changed phenotype.      • A second round of transcription can begin before the preceding transcript is completed.

  29. Self Assessment Question 12 Answer • Which of the following is true regarding gene expression? • Only one gene can be present within a given DNA sequence.      • Mistakes in transcription are corrected by RNA polymerase.      • The ribosome binding site lies at the 3' end of mRNA.      • A change in genotype always results in a changed phenotype.      • A second round of transcription can begin before the preceding transcript is completed.CORRECT ANSWER

  30. WH Freeman, Molecular Cell Biology, 5th Edition, 2004.

  31. Questions?

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