Course number: BIOL 3090 Course title: Cell Biology Class 4 Basic Molecular Genetic Mechanisms Today, we wil learn 1 thing: The central dogma of molecular biology ?How is DNA replicated? ?How is DNA transcribed to mRNA? ?How is mRNA translated to protein? Lodish P102 Fig 4-1 Four basic molecular genetic processes What is the DNA structure? Lodish P104 Fig 4-3 T-A and G-C pairs Lodish P102 Fig 4-1 Four basic molecular genetic processes Flash animation ?The function of DNA polymerase Lodish P13 Fig 4-3 A problem to duplicate the lagging strand: DNA polymerase synthesize DNA only from the 5?- to 3?- direction. Flash animation: DNA replication Order the folowing enzymatic activities required for DNA replication on the laging strand in eukaryotes. One activity is used more than once and another activity is not used at al. 1.Enter answer text... A. DNA polymerase B. RNA polymerase C. DNase D. RNase E. DNA ligase Video Time: DETAILS of replication. Lodish P102 Fig 4-1 Four basic molecular genetic processes Flash movie: RNA polymerase Video Time: DETAILS of transcription. Which way is transcription going? 1.-> left to right 2.<- right to left 1 2 Lodish P102 Fig 4-1 Four basic molecular genetic processes Different RNA processing between Prokaryote and Eukaryote What are they? 1.Operon (prokaryote) 2.The 5?- methylated cap (eukaryote) 3.Splicing (eukaryote) 4.Poly-A tailing Lodish P12 Fig 4-12 Operon A set of proteins is made from a single mRNA 1 mRNA encodes 1 protein What are advantages? Ex: Protein expresion involved in tryptophan synthesis Lodish P13 Fig 4-13 5? methylated cap ?The cap protects an mRNA from enzymatic degradation. ?The cap assists in an mRNA export to the cytoplasm. ?The cap is bound by protein factor required to begin translation. The function of the cap Lodish P13 Fig 4-14 Splicing (eukaryote) What are the advantages ? We wil learn in the Clas 10 Video Time: mRNA splicing - letter editing. Lodish P102 Fig 4-1 Four basic molecular genetic processes Flash movie: Ribosomes Video Time: DETAILS of translation. Lodish P120 Table 4-1 Genetic code 4 x 4 x 4 - 3 = 61 Analyze the data A method used: ?In vitro translation In vitro (transcription) and translation In vitro translation method eficiently translates exogenous RNA from a variety of diferent organisms, from viruses and yeast to higher plants and mamals. The extract (wheat germ or Rabit reticulocyte lysate) is transfered to a smal tube. Both retic and wheat germ extracts translate RNA isolated from cels and tisue or those generated by in vitro transcription (se Figure). When using RNA synthesized in vitro, the presence of a 5' cap structure may enhance translational activity. Typicaly, translation by wheat germ extracts is more cap-dependent than translation by retic extracts. If caping of the RNA is imposible and the protein yield from an uncaped mRNA is low, the coding sequence can be subcloned into a prokaryotic vector and expresed directly from a DNA template in an E.coli cel-fre system. Ad radio-labeled cysteine (Cys) Which initiation codon is recognized by ribosomes better without the hairpin structure? 1. AUG#1 2. AUG#2 3. same What is the function of the secondly structure (hairpin)? 1. Makes ribosomes slow down 2. Makes ribosomes sped up 3. Works as AUG codon 4. Blocks the ribosome movement One base of nucleotide is approximately 0.4 nm. Estimate the width of a ribosome. 1.1.2 nm 2.2.0 nm 3.6.4 nm 4.12.8 nm 5.None of them
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