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Molecular Biotechnology

Subject : engineering
Instructions:
  • Answer 50 questions in 15 minutes.
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  • Match each statement with the correct term.
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This is a study tool. The 3 wrong answers for each question are randomly chosen from answers to other questions. So, you might find at times the answers obvious, but you will see it re-enforces your understanding as you take the test each time.
1. Search for site to start transcription - unwind DNA; -35 region and pribnow region (-10 region).






2. Start codon is usually ATG - first amino acid is n - formyl- methionine. It is assisted by initiation factors (IF) and requires ribosomal binding sites (RBS). It is a polycistronic protein translation (operon).






3. 1. LacI- makes an internal inducer -- NO. Found that lacI- doesn't dominate over lacI+ and is not always constitutive. 2. LacI- is a repressor protein -- YES. LacI+ dominates over lacI- because when both are together - lac operon is inducible. LacI m






4. A strand segment complementary to the template with a free 3'OH group






5. Three sites recruit tRNA and forms peptidyl- tRNA bonds (E - exit; P - peptide; A - acceptor).






6. Need to remove introns before changing into mRNA - then take mRNA out of the nucleus. Has 3 RNAP (RNAP I synthesizes rRNA - II synthesizes mRNA - III synthesizes tRNA and small rRNA). Transcription factors are similar to sigma factors.






7. Genes for products that are required at all times.






8. 1. Ethidium bromide staining 2. P32 - P33 radioactivity 3. Fluorescence 4. Agarose gel electrophoresis






9. LacY: Transports lactose into the cell LacZ: B- galactosidase LacA: transacetylase LacI: lacI+ cells fully inducible - lacI- were already induced and not responsive to IPTG X- gal: analog of lactose that turns blue when cleaved by lacZ product and o






10. When arabinose is present - it binds to araC and allosterically induces it to bind to araI instead araO2. If glucose is absent - then the presence of CAP bound to its site between araO1 and araI helps break the DNA loop and helps araC bind to araI






11. Gene products decrease in concentration under particular molecular circumstances






12. C - N - O - H make up 99% cell weight - 70% is water






13. Inducer site; araC bound at this site can simultaneously bind to the araO2 site to repress transcription from the Pbad promoter. In the presence of arabinose - araC bound at this site helps to activate expression of Pbad promoter.






14. The ribosome translating the leader peptide arrives at the two tryptophan codons and has to wait for tryptophan. During this time - RNAP continues to transcribe. Stem loop between 2 and 3.






15. 1. Initiation: unwind DNA at the origin of replication (ori) - bidirectional replications; regulated as required for cell division 2. Elongation: requires RNA primer to replicate 3. Termination: signaled by Ter sequence






16. 1. Capping: 5' phosphate capped by 7- methyl guanosine and is a 5'-5' linkage instead of 5'-3' This makes RNA more stable 2. Intron removal 3. Export to cytoplasm 4. Polyadenylated mRNA precursor






17. 1. Nucleic acid hybridization: (a) bind single stranded DNA to a membrane support - (b) add single stranded labeled DNA (probe) under appropriate conditions - (c) wash the support to remove excess unbound labeled probe DNA - (d) detect the hybrid seq






18. The small ribosomal subunit binds to 5'-G cap on processed mRNA (no RBS) - uses met instead of fmet for initiation; monocistronic translation






19. Attenuation






20. Binds to CAP binding site. In conjunction with araC bound with arabinose - it assists RNAP in binding to the Pbad promoter






21. The first two bases of the codon always form strong Watson -Crick base- pairing. The first base in the anticodon determines the number of codons a tRNA can recognize. The first position in anticodon is often modified to inosine to facilitate wobble b






22. Operons transcribed as single mRNA and mRNA codes for more than one protein.






23. Replication > DNA > Transcription > RNA > Translation > Protein






24. Production of commercial products generated by the metabolic actions of microorganisms.






25. The repressor dimer (aporepressor) can't bind to the repressor. Transcription from the promoter is not stopped. When tryptophan is bound to the repressor dimer - the repressor changes configuration so that it can bind to the operator and transcriptio






26. Ribosome doesn't stop at trp codons and stem loop forms between 3 and 4. RNAP stops prematurely (attenuated)






27. Codes for three enzymes needed to catalyze the metabolism of arabinose. The operon is regulated by araC gene product.






28. Gene products increase in concentration under particular molecular circumstances






29. A unicellular organism that lacks a nucleus and membrane bound organelles






30. The process in which an exact copy of the double strand DNA is made. It is a templated process and occurs from 5' to 3' end. DNAP - RNA primer; semiconservative (each strand is a template for the replication of the complementary strand)






31. A templated process just like in DNA replication and there is no processing steps.






32. Functions: enzymes - regulation - structural - cellular functions Polymers of amino acids and connected by peptide bonds. Can fold into complex structures.






33. Expression levels rise and fall in response to molecular signals






34. When arabinose is absent - there is no need to express the structural genes. AraC does this by binding simultaneously to araI and araO2 - making a looped DNA. This blocks access to Pbad promoter. AraC is an autoregulator of its own expression and the






35. A cell that contains a nucleus and membrane bound organelles






36. Operator site - araC binds to this site and represses its own transcription from the PC promoter. In the presence of arabinose - araC bound at this site helps to activate expression of Pbad promoter






37. AARS charges the correct amino acid to tRNA in a two- step reaction.






38. Release DNA - rewind DNA - release RNA; stop signals or rho mediated termination (hairpin is a palindromic GC- rich region followed by an AT- rich region; Rho is a termination factor that binds to nascent RNA) RNAP has sigma factor that recognizes pr






39. In prokaryotes - related genes often arrayed in tandem. A unit of bacterial gene expression and regulation - recognized by a regulator gene product






40. 4. Cells + organelle 3. Supermolecular complexes 2. Macromolecules 1. Monomeric units






41. A reading frame without termination codon among 50 or more codons. Usually correspond to genes that encode proteins






42. Comprised of >50 proteins associated with rRNA units. Site of protein synthesis and binds mRNA and finds protein synthesis initiation sites. It also binds aa- tRNA and catalyzes peptide bond formation.






43. Important to suppress mutations at 3rd position and you don't need to have a lot of stop codons; cells can be more flexible






44. Multiple effects from a single gene






45. Nonsense mutation in gene that results in truncated protein can be lethal. Sometimes a second mutation arises that counteracts the effects of the mutation. Amber stop codon (UAG/TAG/etc) and amber suppressor tRNA (CUA/etc) can restore protein size an






46. EF-Tu GTP binds with an aminoacyl- tRNA and brings it to the ribosome. Once the correct aminoacyl- tRNA is positioned in the ribosome - GTP is hydrolyzed and EF-Tu* GDP dissociates away from the ribosome






47. The process of increasing the expression of inducible genes






48. Determines amino acid selection. A noncognate amino acid charge incorrectly to the tRNA will be inserted into the protein. Introduce new amino acid by using tRNA for UAG.






49. In E. coli - DNAP III can unwind DNA (helicase) and replicate both strands of DNA. It also has proofreading activity and corrects mistakes 3' to 5' exonuclease






50. Select correct ribonucleotides; loss of sigma factor - transcription bubble - no need for primers