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Biochemistry 2280A Lecture Notes - Lecture 21: Aminoacyl-Trna, Start Codon, Genetic Code

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mauveserval406
22 Sep 2020
School
Western University
Department
Biochemistry
Course
Biochemistry 2280A
Professor
Brian Dempsey

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Document Summary

Lecture notes: the decoding of the mrna to produce a protein occurs on the ribosome, this process of translation is complex, requiring many rna and protein factors. Genetic code: the mrna spells out the amino acid code in 3 letter words called codons, each protein has a specific reading frame that is determined by where the decoding process begins. Ribosomes: protein synthesis occurs on large multimeric protein rna complexes called ribosomes, ribosomes have 2 subunits, large and small, the small and large subunits are composed of both rna (rrna) and protein. Initiation is the key step in deciding whether an mrna is to be translated: translation begins at an aug codon and with a special initiator trna that carries methionine (met) In this process the initiator trna is positioned at the p site. Ef-tu will only release the trna to the ribosome if the anticodon of trna matches the codon of the mrna.

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Related Questions

20. Compare and contrast the events that must take place to form the open complex in prokaryotes and eukaryotes.

21. Describe in detail the function of a “promoter” in transcription. Where is its location? Explain how the factor recognizes promoters.

22. Describe the 2 mechanisms of termination of transcription in E. coli.

23. What is the function of histone acetyltransferases and histone deacetylases? Explain what the result would be if an organism could not produce functional histone deacetylases.

24. What is the function of the 5’ Cap and poly A tail in eukaryotic Pre-RNA’s?

25. What is alternative splicing? How can it be advantageous to an organism? Be sure to include in your discussion exons and introns.

26. How does an amino acid become attached to a tRNA molecule? What mechanism ensures amino acids get attached to the correct tRNA

27. What is meant by the phrase “the genetic code is termed degenerate”? What is the “wobble base” and why is it called this?

28. One of the fundamental tenets of translation is that codons are read in triplets. Discuss the experiment that proved the genetic code is read in triplets.

29. Describe the structure of ribosomes and how they are assembled.

30. Describe the stages of Translation-Initiation, Elongation and Termination.

22. What is probably the single most important distinction between bacteria and eukaryotes?

a. transcription

b. the separation of the cell's genetic material from the surrounding cytoplasm

c. the existence of ribosomes

d. RNA processing in bacteria

e. antibiotics

23. Which one does NOT characterize an open reading frame (ORF)

a. Uses six reading frames during translation

b. Contains a start codon

c. Contains a stop codon

d. Its length is in multiples of 3 nucleotides

e. It should have the number of codons for a protein or on average ~250 codons in length.

24. Nested intronic genes lie within the non-coding intronic region of a larger gene, and occur in the human genome.

a. True

b. False

25. How would you characterize this statement: EF-Tu will hydrolyze GTP only if the codon:anticodon & tRNA:amino acid matchings are correct

a. Transcription; initiation steps

b. Transcription; termination steps

c. Translation: initiation steps

d. Tanslation: elongation steps

e. Spliceosome

26. Regarding the transcription unit architecture of the Escherichia coli genome, which one is FALSE?

a. Each of the 4,661 transcription units comprised an average of 1.1 modular units.

b. 3,010 transcription units (~65%) are monocistronic.

c. 1,652 transcription units (35%) contain more than one ORF (polycistronic)

d. The largest transcription unit is equivalent to 16 ORFs with numerous introns.

e. 398 transcription units (~9%) are nested within each other in opposite transcriptional orientation

27. Regarding RNA interference (RNAi), which one is FALSE?

a. It is a common and conserved mechanism in eukaryotic cells.

b. Originally discovered in bacteria and plant viruses.

c. A form of primitive immunity to protect the genome.

d. Pre microRNA (miRNA) genes have been found in introns.

e. Recent research shows that exogenous plant miRNAs in food can regulate the expression of target genes in mammals.

28. Aminoacyl-tRNA synthetases

a. Recognize the 3’UTR

b. The genes for these enzymes fall into the family of inducible genes

c. The enzymes are imported into the nucleus

d. Covalently attaches an amino acid to the appropriate tRNA. This takes place in the cytoplasm.

e. Forms the peptide bond during protein synthesis

29. What is the process by which complementary RNAs are made from a DNA template?

a. translation

b. transcription

c. protein synthesis

d. transduction

e. transliteration