mod 5

• The sequence of mRNA molecule corresponds to part of the chromosome
• Transcription

  One strand in part of the chromosome is copied into a complementary RNA molecule by RNA polymerase
• DNA information is first converted to RNA
• Specialized sequences outside of the transcribed region provide the information for transcription: regulatory sequences, promoter, terminator
• The central dogma of molecular biology is a linear, unidirectional transfer of genetic information from DNA to RNA to protein
• Initiation stage of Transcription

  • Promoter: RNA polymerase initially binds here. Binding facilitated by transcription initiation factors which bind to special sequences at the promoter
• Jacob and Monod proposed that unstable RNA molecules code for the amino acid sequences of proteins, known as messenger RNA (mRNA)
• Transcription is "like" DNA replication, but only one strand is copied and ribonucleotide triphosphates are used instead of deoxyribonucleotides
• Genes correspond to small regions of chromosomes bounded by specialized sequences
• During Transcription, RNA polymerase initially binds to the promoter
• Transcription is a process where one strand of the chromosome is copied into RNA by RNA polymerase
• Transcription can be regulated by specialized sequences like regulatory sequences, promoter, terminator
• Pulse chase experiments involve "Pulsing" with radioactive ribonucleotides, then chasing with non-radioactive nucleotides to track the movement of radioactivity
• Genes code for polypeptides
• Only some regions of chromosomes are transcribed into RNA
• Elongation stage of Transcription

  • Synthesis of RNA by RNA polymerase moving along the DNA
• Transcription

  • Can be divided into three stages: Initiation, Elongation, Termination
• Infection of E.coli with bacteriophage T2 results in synthesis of RNA molecules with a base composition similar to the T2 chromosome, suggesting that T2 DNA is being converted to RNA
• Transcription is divided into three stages: Initiation, Elongation, Termination
• Synthesis of RNA occurs during the Elongation stage of Transcription
• Deletion of positive acting elements will result in loss of gene expression. Deletion of negatively acting elements will result in up-regulation or inappropriate (ectopic) gene expression
• Operons in prokaryotes allow more than one gene to be transcribed from the same promoter. Genes in an operon often have related functions
• Termination

  Termination signal tells RNA polymerase to fall off the DNA
• Initiation

  RNA polymerase initially binds at the Promoter, facilitated by transcription initiation factors which bind to special sequences at the promoter
• Consensus sequence for -35 region is TTGACAT, and for -10 region (Pribnow box) is TATAAT. Both are bound by σ factor
• Transcription

  Can be divided into three stages: Initiation, Elongation, Termination
• Elongation

  Synthesis of RNA by RNA polymerase moving along the DNA
• Bacterial promoter has two distinct elements: -35 region and -10 region
• Identifying key non-coding regions in DNA

  Compare sequences of regions in the genome performing a similar function and identify similarities. Delete or mutate regions to determine the effect on gene expression. Identify proteins that bind to specific regions in the genome
• Strong E. coli promoters have a consensus sequence of TTGACAT for the -35 region and TATAAT for the -10 region
• ORF = open reading frame
• Translation

  Ribosomes: Key features and function
• Translation

  Translation elongation and termination
• Translation

  Function and structure of tRNAs – charging by aminoacyl tRNA synthetases
• From DNA to inherited traits

  mRNA
• Translation

  Translation requires: mRNA, tRNA, Intermediate (“Adaptor”) binds to mRNA and amino acid, Aminoacyl tRNA synthetases charge tRNAs with amino acids, Ribosome catalyzes synthesis of a polypeptide, Accessory proteins initiation, elongation, termination factors
• Adaptor = tRNA
• Genes correspond to discrete regions of DNA
• From DNA to inherited traits

  RNA sequence – decoded into amino acid sequence – polypeptide (protein)
• From DNA to inherited traits